On the Road to Sustainable Energy Supply in Road Transport – Potentials of CNG and LPG As Transporta- Tion Fuels

On the road to sustainable energy supply in road transport – potentials of CNG and LPG as transporta- tion fuels

Short study in the context of the scientific supervision, support and guidance of the BMVBS in the sectors Transport and Mobility with a specific focus on fuels and propulsion technologies, as well as energy and climate Federal Ministry for Transport, Building and Urban Development (BMVBS) AZ Z14/SeV/288.3/1179/UI40

Main contractor: Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR) Institut für Verkehrsforschung Rutherfordstraße 2, 12489 Berlin Tel.: 030 67055-221, Fax: -283

Subcontractors: Institut für Energie- und Umweltforschung Heidelberg GmbH (IFEU) Wilckensstraße 3, 69120 Heidelberg Tel.: 06221 4767-35 Ludwig-Bölkow-Systemtechnik GmbH (LBST) Daimlerstraße 15, 85521 München/Ottobrunn Tel.: 089 608110-36 Deutsches Biomasseforschungszentrum gGmbH (DBFZ) Torgauer Straße 116, 04347 Leipzig Tel.: 0341 2434-423

Authors C. Heidt, U. Lambrecht (IFEU), M. Hardinghaus, G. Knitschky (DLR), P. Schmidt, W. Weindorf (LBST), K. Naumann, S. Majer, Dr. F. Müller-Langer, Dr. M. Seiffert (DBFZ)

Heidelberg, Berlin, Munich, Leipzig, 26 September 2013

Summary

Liquefied petroleum gas (LPG, ‘Autogas’) and compressed natural gas (CNG) are the most common alternative fuels for motor vehicles worldwide. A number of countries subsidise the utilisation of gaseous fuels in the transport sector for reasons including environmental benefits, diversification of the fuel market and the reduction of supply dependency. In Germany, CNG and LPG are subsidised with a reduced mineral oil tax rate under the German Energy Tax Act (EnergieStG) until the 31.12.2018. In association with the Mobility and Fuels Strate- gy of the German Federal Government, the present short study investigated the utilisation of CNG and LPG in motor vehicles to inform the current debate on the possible extension of the present subsidies. The focus is on recent and future developments of both the market and associated environmental impacts in Germany. The following conclusions arise:

1. Despite competitive costs, CNG and LPG vehicles account for a low proportion of the current overall stock. Financial benefits have resulted primarily in conversion of petrol to LPG cars. The total costs of ownership (TCO) of both CNG and LPG vehicles are competitive in comparison to conventional engines (diesel / petrol) in the present tax framework. However, according to the German Federal Motor Transport Authority (KBA), CNG and LPG vehicles account for approx. 1% of the total German vehicle stock (status in 2012). The majority are petrol cars that were converted to LPG. CNG on the other hand is utilised more frequently in production-line vehicles in the car and commercial vehicle sectors.

Without energy tax benefits, the TCO would be higher compared to diesel vehicles in most cases. Thus, new registrations and conversion rates are expected to further decline without subsidies after 2018. Yet, the present situation also indicates that TCO competitiveness is only in part responsible for the overall acceptance and sales figures of CNG and LPG vehicles. To further promote implementation, a number of additional measures are required. These include improved consumer information, extension of the range of vehicles on offer and concerted efforts to improve the fuelling station infrastructure.

2. The utilisation of CNG and renewable methane instead of petrol or diesel may reduce road transport emissions of greenhouse gases (GHGs) and pollutants. In contrast, LPG offers fewer environmental benefits than CNG, and lacks overall potential for integration of renewable energies. CNG engines are currently associated with the lowest environmental impacts among current powertrains. A natural gas vehicle operated with fossil fuels is generating the lowest GHG emissions (-15 % in comparison with petrol cars). However, substantial GHG savings may be achieved with the utilisation of biomethane (up to -66 % compared to petrol). The GHG emissions of LPG vehicles show a modest -9% reduction. Page 3 of 79 A look at the emission of pollutants reveals that both CNG and LPG vehicles compare favourable to diesel vehicles, in particular with respect to NOX emissions (TTW). In contrast, LPG produced from crude oil is at a disadvantage compared to conventional fuels with respect to NMHC und SO2 emissions, which ensue primarily during fuel supply (WTT).

Future potentials for the reduction of environmental burdens are greatest for CNG. Increas- ing use of hybrid technology in vehicles is expected to result in reduced fuel consumption rates. These advances in fuel efficiency could be more pronounced for CNG than for petrol or diesel engines. Furthermore, CNG engines may utilise renewable methane from additional supply pathways, e.g. synthetic methane derived from biomass or renewable electricity. If the development of the renewable energy sector is accelerated, additional and surplus capacities of renewable electricity could be utilised to produce synthetic, so-called ‘RE methane’. For LPG, no novel renewable pathways ready for the market are expected at present. Nonethe- less, mid-term advantages of LPG would include an additional diversification of the energy supply in road transport. LPG in Germany is primarily produced from crude oil at present; however, it may also be obtained from natural gas.

Promising applications for CNG may also be found in the commercial vehicle sector, which is still dominated by diesel engines at present. Low exhaust emissions in CNG vehicles are particularly beneficial in cities, and CNG city buses are already common. Moreover, the CNG infrastructure may be able to contribute to the future fuel supply for long-distance freight transport with liquefied natural gas (LNG).

3. Individual subsidisation of CNG and LPG may contribute to the sustainable energy supply of the transport sector. In this context, the framework should target long- term integration of renewable energies. In the case of future subsidisation, renewable energy potentials of CNG should be considered above all. Thus, individual energy tax rates or statutory blending quotas may promote renewable fuels in particular. Although CNG from fossil natural gas is associated with fewer environmental benefits, tax benefits in the coming years would support both the development of the CNG vehicle market and the CNG infrastructure. These measures could facilitate the integration of renewable energies, e.g. biomethane and methane derived from renewable electricity, into road transport.

There is less overall support for continued subsidisation of LPG. However, LPG greenhouse gas emissions are lower than those of petrol, and the contribution to the diversification of the fuel sector could be taken into consideration in the subsidy extension debate. Energy taxation could follow the principles of the EU alternative fuels strategy, i.e. seek to differentiate between CO2 and GHG emissions.

Page 4 of 79 Table of contents

Summary ...... 3

1 Background and aims of the study ...... 10

2 Market situation of natural gas vehicles ...... 11

2.1 Overview ...... 11

2.1.1 Fuel properties and engine technology ...... 11 2.1.2 Range of models ...... 12

2.2 Vehicle stock ...... 12

2.2.1 Development to date ...... 12 2.2.2 Current trends for registration of CNG and LPG vehicles ...... 13

2.3 Comparison of costs and perspectives for passenger cars ...... 14

2.3.1 Methodology for full cost accounting ...... 14 2.3.2 Comparison of the full cost for new vehicles and conversions ...... 15 2.3.3 Future perspectives for the vehicle stock ...... 17

3 Environmental comparison and potentials for renewable energies...... 19

3.1 Structure of the environmental comparison ...... 19 3.2 Fuel supply – Well-to-tank (WTT) ...... 21

3.2.1 Overview of the emission factors under investigation ...... 21 3.2.2 Comments on fossil fuel production and supply...... 23 3.2.3 Comments on renewable fuel production and supply ...... 23

3.3 Vehicle operation – tank-to-wheel (TTW) ...... 30

3.3.1 Vehicles under investigation ...... 30 3.3.2 Fuel consumption ...... 31 3.3.3 Greenhouse gas and pollutant emissions ...... 36

3.4 Well-to-wheel (WTW) comparison 2012 ...... 39

3.4.1 Greenhouse gas emissions ...... 39 3.4.2 Primary energy consumption and pollutant emissions ...... 44

3.5 Well-to-wheel (WTW) comparison 2030 ...... 47

3.5.1 Greenhouse gas emissions ...... 47 3.5.2 Primary energy consumption and pollutant emission ...... 49

4 Perspectives for the promotion of CNG and LPG in road transport ...... 52 Page 5 of 79 4.1 Benefits from an environmental perspective ...... 52 4.2 Potential subsidy framework ...... 53

Appendix I: Amortisation potential of LPG conversion for the German petrol vehicle fleet .... 55

Appendix II: Well-to-tank calculations ...... 56

Methodology ...... 56

Physical energy content method ...... 56 Allocation of byproducts ...... 56 Embodied energy ...... 57 Other impact categories ...... 57

Fossil fuels ...... 57

Petrol and diesel from crude oil ...... 57 Petrol and diesel from tar sands ...... 60 CNG from natural gas ...... 61 LPG from crude oil/natural gas ...... 63

Renewable fuels ...... 69

Biomethane ...... 69 Synthetic methane from renewable electricity (RE methane) ...... 72

Appendix III: Energy taxation for fuels ...... 74

Literature ...... 75

Page 6 of 79 Table of figures

Figure 1: Development of the natural gas vehicle stock in Germany ...... 13

Figure 2: Comparison of the average full cost depending on type of drive of new vehicles in the B-segment small cars ...... 15

Figure 3: Range of amortisation of LPG conversion (1800-3500 €) depending on mileage and consumption ...... 17

Figure 4: Schematic of the environmental comparison ...... 19

Figure 5: Biofuels subject to energy tax benefits credited to the quota in 2011 and 2012 (DBFZ based on BLE 2013 and BAFA) ...... 26

Figure 6: Methanation of H2 from electricity utilising CO2 from biogas upgrading ...... 28

Figure 7: Exemplary comparison of CO2 emissions and relevant vehicle design of selected passenger cars ...... 33

Figure 8: WTW Greenhouse gas emissions for passenger cars in 2012 ...... 39

Figure 9: Comparison of the CO2 benefits of CNG and LPG from fossil supply pathways for motors cars in 2010/2012 in recent studies ...... 41

Figure 10: WTW greenhouse gas emissions of city buses in 2012 ...... 43

Figure 11: WTW pollutant emissions of passenger cars in 2012 ...... 44

Figure 12: WTW pollutant emissions for city buses in 2012 ...... 46

Figure 13: WTW greenhouse gas emissions for passenger cars in 2030 ...... 47

Figure 14: WTW greenhouse gas emissions for city buses 2030 ...... 48

Figure 15: WTW pollutant emissions for passenger cars 2030 ...... 49

Figure 16: WTW pollutant emissions for city buses in 2030 ...... 51

Figure 17: Energy tax losses and GHG savings in relation to a petrol vehicle in 2012 (Calculation in Appendix III) ...... 52

Figure 18: Potential of conversion to LPG for the German vehicle fleet ...... 55

Figure 19: Crude oil refinery ...... 68

Page 7 of 79 List of tables

Table 1: CO2 emissions from fuel combustion ...... 20

Table 2: Overview of energy consumption and emissions WTT ...... 22

Table 3: Overview of the marketability of the renewable supply pathways under investigation ...... 24

Table 4: ‘Dumped energy’ according to German Network Development Plan [NEP 2013, p. 64, Table 9] ...... 27

Table 5: Fuel consumption of a small family car (Golf class) in the NEDC after JEC 2011 ...... 32

Table 6: Fuel consumption of average passenger cars in 2012 and 2030 ...... 35

Table 7: Fuel consumption of average city buses in 2012 and 2030 ...... 36

Table 8: Emission factors for greenhouse gases TTW ...... 37

Table 9: Emission factors for air pollutants TTW ...... 38

Table 10: System boundaries and fundamental assumptions of recent studies on environmental comparisons of CNG/LPG with other fuels ...... 40

Table 11: Supporting framework for the subsidisation of CNG and LPG ...... 54

Table 12: Energy flows and emissions from crude oil production ...... 58

Table 13: Energy flows and emissions from crude oil transport ...... 58

Table 14: Energy flows and emissions from the production of petrol and diesel in oil refineries ...... 59

Table 15: Fuel consumption and GHG emissions of an inland waterway vessel ...... 59

Table 16: Energy flows and emissions from the production of synthetic crude oil (SCO) from tar sand deposits in Canada ...... 60

Table 17: Fuel consumption and GHG emissions of an oil tanker ...... 61

Table 18: Energy flows and emissions from the production and processing of natural gas ...... 62

Table 19: Energy flows and emissions from transport of natural gas over great distances ...... 62

Table 20: Natural gas consumption and emissions from gar turbines of natural gas compressors ...... 63

Page 8 of 79 Table 21: Energy flows and emissions for the production and processing of LPG ...... 64

Table 22: Fuel qualities of LPG...... 65

Table 23: LPG transport vessel “Djanet“ [Kawasaki 2000] ...... 65

Table 24: Fuel consumption and emissions of a 40 t lorry ...... 67

Table 25: Energy demand and emissions from LPG production in a crude oil refinery ...... 68

Table 26: Overview of data for ecological parameters of biomethane supply ...... 70

Table 27: Parameters of the examined concepts for biomethane production from renewable resources/liquid manure and biodegradable waste [Biogasrat 2011] ...... 71

Table 28: Input/output data for the production of methane from CO2 and hydrogen

(incl. CO2 supply) ...... 73

Table 29: GHG savings costs for energy tax benefits in comparison to petrol ...... 74

Page 9 of 79 1 Background and aims of the study

Natural gas (CNG) and liquefied petroleum gas (LPG, ‘Autogas’) are subsidised with a reduced mineral oil tax rate under the German Energy Tax Act (EnergieStG) until the 31.12.2018. Public debate on the extension of these subsidies beyond 2018 is already under way. The present study aims to compile facts, arguments and requirements in favour of and against the extension of subsidies of the two energy carriers. The scope includes the following sections:

Technologies and associated costs of CNG and LPG in comparison with diesel and petrol vehicles based on the status quo, yet including future perspectives. Development of the CNG/LPG fleet in road transport to date, including an assessment of the potential influence of changes to current parameters on the development of future vehicle stock. Illustration of promising supply pathways for renewable methane including benchmark values for typical GHG and pollutant emissions, complemented by a discussion of the present and future market perspectives of biomethane and RE methane on the fuel market. Comparison of the environmental impacts of CNG and LPG vehicles with respect to established and alternative fuel supply pathways today (2012) and in the future (2030). Discussion of the perspectives of CNG and LPG vehicles to advance integration of renewable energies into the road transport sector. Points argued in favour of and against further energy tax benefits of CNG/LPG beyond 2018, or rather necessary pre-requisites for such measures (e.g. based on renewable energies and sustainability criteria).

Page 10 of 79 2 Market situation of natural gas vehicles

2.1 Overview

2.1.1 Fuel properties and engine technology

LPG (Liquefied Petroleum Gas), also known as autogas, consists primarily of the hydrocarbons propane and butane. These arise as byproducts of natural gas and crude oil production. The physical properties of LPG do not significantly differ from those of petrol (with the exception of density), and LPG may be utilised as fuel in modified petrol engines. The liquefaction of LPG is relatively simple (at 8 to 10 bar), thus facilitating storage and trade.

CNG (Compressed Natural Gas) or natural gas has a chemical composition of over 80 % methane. In Germany, it is offered as H-Gas or L-Gas which differ in methane content and heating value. At 200 bar, the compressions of natural gas for storage purposes on board the vehicle requires higher pressure levels than LPG. For this reason, CNG is carried in a pressure tank. Complex technology is required for the alternative liquid storage as Liquefied Nat- ural Gas (LNG), as it requires cooling at -161.5°C. Compressed natural gas has a heating value per kg similar to petrol, and is utilised in modified petrol engines.

The higher anti-knock capacity of CNG (octane number 120) allows combustion in CNG- optimised engines with higher compression levels, thus resulting in higher energy efficiency in comparison with LPG and petrol (octane number ≤100) [Stan 2005]. However, CNG fuel storage under high pressure requires measures obsolete for LPG, i.e. solid large-volume containers and high-pressure control of engine supply. In contrast, LPG may achieve better mileage at relatively low pressure levels with small tank volumes.

LPG vehicles commonly pursue a bi-fuel concept, i.e. the vehicles are equipped with both LPG and petrol tanks. In contrast, CNG vehicles are offered as bi-fuel or dedicated drives, the latter being equipped with a small emergency petrol tank only.

Conversion from petrol to gas operation requires an additional pressurised tank, a separate injection system with hoses fitted with a pressure gauge and an appropriate engine management. Due to differences in storage pressure, bi-fuel drive with CNG and LPG is not possible. Conversion costs for vehicles are much lower for LPG than for CNG. Technological advances allow injection with internal or external mixture formation. In this context, modification with direct injection is more elaborate. The conversion of diesel engines is also possible. However, the fact that spontaneous combustion requires the installation of an ignition system renders conversion distinctly more expensive and rarely viable from an economic angle.

Page 11 of 79 2.1.2 Range of models

The range of models on the market for gas vehicles to date is very limited. In Germany, 44 LPG models from 25 model ranges are available for order, whereas 21models from 12 model ranges are available for purchase with CNG drive (status 07/2012). A selection of additional vehicle features and options is virtually non-existent. The majority of vehicles on offer belong to the MPV segment, or the small and large family car segments. The current vehicle market is characterised by a multitude of options for vehicle body and equipment. Thus, the limited selection for gas vehicles may prevent overall popularity and growing expansion.

2.2 Vehicle stock

2.2.1 Development to date In 2011, the global number of natural gas vehicles registered was about 15 million [NVGA 2012]. Gas vehicles represent a high proportion of the total vehicle stock in Pakistan, Bang- ladesh, Armenia, Iran, Bolivia and Argentina. The global market development for gas vehicles is generally much more than dynamic compared to the situation in Germany. This trend is driven by considerable expansion in Iran, China and Pakistan as well as by emerging markets in a number of newly industrialised countries.

The global number of vehicles operated with LPG in 2010 was about 17.5 million [WLPGA 2011]. Demand for LPG is also dynamic (+59 % between 2000 and 2010) with a small number of countries acting as major drivers of the demand. The most important markets are in Poland, Turkey and Korea. With the exception of Korea, where a great number of LPG cars are production-line vehicles, the great majority of LPG cars are converted petrol vehicles. In the segment of heavy-duty commercial vehicles, LPG drives are rare due to the elaborate conversion procedure involved. The global trend for countries with a well-developed fuelling station infrastructure and established refineries is an increased integration of LPG due to the low costs for modification and production. Countries with natural gas deposits (and poorly developed infrastructure) tend to favour natural gas.

In Europe, natural gas vehicles have a high market share in Italy and Bulgaria (see [NGVA Europe 2012]). Furthermore, a considerable number of CNG vehicles is operated in Germa- ny and Sweden. According to WLPGA, the most important markets for LPG vehicles are in Europe are in Poland and Italy (see [WLPGA 2011]).

According to the German Federal Motor Transport Authority, as of 01.01.2012 about 75,000 CNG vehicles and 455,000 LPG vehicles were registered, respectively. This is representative of a proportion of 1.2 % of the total stock. A further 18,000 commercial vehicles are operated with CNG, whereas the number of LPG commercial vehicles comes to 8700. Most CNG commercial vehicles are registered in the category of light commercial vehicles below a two

Page 12 of 79 ton payload. Among heavy-duty commercial vehicles, operation with gas is virtually non- existent except for CNG city buses.

Figure 1: Development of the natural gas vehicle stock in Germany

2.2.2 Current trends for registration of CNG and LPG vehicles

In recent years, the trend for increases in LPG vehicles has distinctly shifted from new registrations to conversions. In this context, the new registration of LPG cars fell below 5000 vehicles, or 0.15 % of all new registrations, in 2011. Simultaneously, conversion numbers reached 95,000, thus representing over 95 % of the increase in LPG cars. Hence, the overall increase remains constant. However, the increasing age of the LPG fleet was responsible for an increase in end-of-life vehicles. For this reason, the overall stock increase was slowed.

The year 2012 saw a significant increase in LPG new registrations against the trend of recent years. Despite this increase, the increase of vehicle stock was slower. Data on vehicle conversion and end-of-life for 2012 are not yet available. Therefore, conclusive evaluations of the newest trends in vehicle stock development are as yet unfeasible. Slightly lower levels of conversions among new registrations and a growing number of end-of-live vehicles may be expected.

The quota of end-of-life vehicles is expected to rise in the coming years from 13.5 % to 19 % of the total stock due to an ageing fleet. Without a significant increase in new registrations,

Page 13 of 79 projections for future trends are likely to predict low growth or virtual stagnation of the LPG fleet.

The development of the CNG fleet is not characterised by such obvious trends. In contrast to LPG, the market for conversion is very small. New registrations of CNG vehicles account for about 0.2 % of the annual new registrations. The year 2012 saw a further decline in the growth of the CNG vehicle stock. Evidently, increasing numbers of end-of-life vehicles and a decrease in new registrations are equally relevant factors in the CNG fleet. Thus, the trend points towards a stagnation of the CNG vehicle stock. However, future developments in the range of models on the market or changes to the tax framework are likely to influence the fleet growth. The factors are discussed in the following chapter (see Chapter 2.3.3).

2.3 Comparison of costs and perspectives for passenger cars

2.3.1 Methodology for full cost accounting

The calculations for the comparison of costs depending on the type of drive for new vehicles are based on data from the ADAC car cost database (effective July 2012). Factors examined include loss of value without interest, maintenance costs (e.g. oil changes and inspections including common wearing parts and consumables, expenses for new tyres), insurance pre- miums for collision damage waiver and comprehensive cover with a 50 % no-claims dis- count, motor vehicle tax as well as fuel costs according to manufacturer data after ECE R841.

Fuel costs are assumed to remain constant over an operation period of four years. Energy tax benefits in force until 31.12.2018 are included according to the German Energy Tax Act of 15.07.2006 (EnergieStG), §2 (2)2. For the comparison of full costs under full taxation, regular energy tax rates according to EnergieStG §2 (1) 7 and 83 and resulting higher VAT levels are calculated. Biomethane is commonly sold at the same price as CNG, thus no distinction is made. To illustrate the influence of differences in taxation, the full costs of diesel engines with a mineral oil tax similar to petrol are included.

To simplify comparisons, vehicles with available gas drive are structured in segments following the classification of the German Federal Motor Transport Authority. Modelling of the average price per segment reduces the influences of price policies of individual manufacturers. The small car segment presents the most diverse range on offer with 12 models or versions from eight manufacturers. Thus, this segment exemplifies the actual market situation most

1 Fuel prices: Diesel 1.45 €/L, Normal/Super 1.60 €/L, SuperPlus 1.69 €/L, LPG 0.81 €/L, CNG 1.03 €/kg, Ethanol 1.15 €/L 2 13.90 €/MWh gaseous hydrocarbons; 180.32 €/t liquid gas 3 31.80 €/MWh gaseous hydrocarbons; 409.00 €/t liquid gas

Page 14 of 79 accurately.

In the full cost accounting of the present study, the probability density function of the annual mileage in the respective vehicle segment interferes with calculation of the full cost. Hence, the level of utilisation is reported for the purpose of assessing the comparison of cost in reference to the actual utilisation. In addition, the quartiles of the mileage distribution are reported. These distributions are derived from data reported in the study [Mobilität in Deutsch- land 2008].

2.3.2 Comparison of the full cost for new vehicles and conversions

The average full cost of the different types of drive in the B-segment is illustrated in Figure 2. Cost differences for the average annual mileage are generally very slight. The full cost associated with an annual mileage of 15,000 km for CNG and LPG engines in the small car segment over four years is approx. 300 € below petrol engine costs and approx. 150 € below diesel. In case of full energy taxation, average CNG/LPG costs in the segment would exceed the cost of diesel but not those of petrol.

Figure 2: Comparison of the average full cost depending on type of drive of new vehicles in the B-segment small cars

The comparison of costs between types of drive in individual cases is complicated by differing costs depending on engine model and size, but primarily obscured by the price policy of the individual manufacturers. Different types of drive are positioned and promoted differently

Page 15 of 79 on the market. The surcharge for LPG may range between 5.5 % and 26 % of the petrol vehicle price (list prices 07/2012). The purchase of an LPG vehicle is generally less expensive than a diesel car. However, a competitive offer for a diesel vehicle may render the full cost over four years more economical than the LPG engine. In contrast, LPG cars are generally more economical over four years in comparison with petrol, except in isolated cases with very low mileage. CNG vehicles are also subject to a highly variable price policy (2000 to over 5000 € surcharge). Thus, the purchase costs of CNG engines in some cases exceed those of a diesel car, yet CNG cars are more economical. However, the calculations further reveal that for some models, the CNG version is currently less economical than the diesel engine. The comparison of full costs associated with type of drive differs depending on manufacturer, model and annual mileage. In consequence, diesel or petrol engines may compare favourably in some cases. The buyer of a new vehicle may struggle to identify potential savings in the individual case.

Relevance of commercial registrations and company vehicle taxation

The German new vehicle market is dominated by commercial new registrations. In 2012, almost 62 % of new registrations were commercial customers (see [KBA 2013]). It is common practice for the drivers of these company cars to select their vehicles. Current legislation on the taxation of company cars includes the new vehicle list price, taxing 1 % of this price as an employee fringe benefit in addition to taxable monthly income. Thus, the costs for the driver are proportional to the original price, but not the running cost. In consequence, there is an incentive to select inexpensive models, whereas economy of consumption is ignored. Taxation of company cars according to consumption or emission levels could generate a distinct shift towards the new registration of gas vehicles. The differences in commercial registrations depending on the segment are noticeable. Equal registration numbers of private and commercial cars are reported only in the small car segment. In higher segments, the proportion of commercial cars clearly prevails. In consequence, there are hardly any higher segment gas vehicles on the market.

The conversion of petrol vehicles to LPG services a different market. The specific mileage that renders conversion economically viable strongly depends on consumption and conversion costs. Figure 3 illustrates the range of mileages to amortisation of an LPG system with conversion costs between 1800 and 3500 € depending on fuel consumption. The vertical range of the amortisation area reflects the conversion cost. For instance, the conversion of a vehicle with a consumption of eight litres breaks even after a mileage between 33,000 and 65,000 km, depending on engine model and associated conversion cost. In this context, the conversion costs of older, simpler engine models are lower than those for engines with sophisticated injection technology. It is evident that conversion is particularly beneficial in vehi-

Page 16 of 79 cles with high consumption. An analysis of the conversion potential of the German passenger car fleet reveals that 20 % of the current petrol car stock would break even within two years4 of LPG conversion. The actual conversion rate of petrol cars, however, is as low as 0.3 %. Thus, the cost advantages of conversion to LPG are practically ignored at present.

Figure 3: Range of amortisation of LPG conversion (1800-3500 €) depending on mileage and consumption

2.3.3 Future perspectives for the vehicle stock

The future costs of gas vehicles versus conventional passenger cars depend on a number of factors. These include differences in fuel and technology costs, but also prevailing price policies and model ranges of individual manufacturers.

At present, fuel prices are strongly influenced by differences in energy taxation. Thus, subsidisation policy is going to define future fuel costs of CNG and LPG in comparison with conventional vehicles. The current framework on average favours diesel engines for new vehicles if no tax benefits apply. However, CNG and LPG may be more economical in individual cases depending on manufacturer and mileage. Overall, the expiry of existing tax benefits is going to put an end to the savings associated with gas engines for the driver. In consequence, a decrease in new registration numbers may be expected. In contrast, LPG conversion is going to retain its amortisation potential for a major proportion of the fleet regardless

4 The time period to amortisation was calculated based on mileage after [MiD 2008] and [Polk 2008] depending on the type of engine (see Appendix I for details)

Page 17 of 79 of tax benefits. This particularly applies to vehicles with high consumption, high mileage and simple engines. Future engines on the market are expected to be fuel-efficient petrol engines with complex technology. Thus, the conversion potential is greatest in the midterm. Ultimate- ly, developments on the global market for liquid and gaseous fuels are going to define future fuel pricing. A prognosis for the global market is fraud with uncertainty and thus outside the scope of the present study.

The comparison of full costs for new vehicles reveals a considerable range. Depending on model and mileage, significant savings or additional costs for CNG/LPG in comparison with other types of drive could be detected. In addition to fuel prices, future competitiveness of CNG/LPG vehicles will depend on both the model range of offer and the price policy of the individual manufacturer. The trajectory for the market is difficult to predict. However, existing legislation on environmental aims may promote future benefits for CNG/LPG vehicles. In this context, CNG vehicles offer a relatively convenient and technologically simple option for manufacturers to significantly reduce CO2 emissions and comply with CO2 fleet targets. The second half of 2012 saw the introduction of four new CNG models to the market with further new releases announced. Greater variety and choice among CNG/LPG vehicles could support competitiveness with other types of drive, as well as attract customers to favour gas vehicles.

Furthermore, the exhaust emission standard Euro 6 is going to come into force in 2015. In consequence, exhaust emission control will have to be adapted to reflect stricter nitrogen oxide regulations, in particular for diesel engines. The additional cost may be transferred to the customer, potentially reducing or even cancelling out cost advantages of diesel vehicles over gas drives.

However, perspectives for the future of gas vehicle stocks may not be reduced to consideration of costs alone. To date, this has been demonstrated in the development of CNG/LPG new registrations and the overall low utilisation of the LPG conversion potential in the fleet. In other words, even energy tax benefits for gas fuels have not been instrumental in promoting a major establishment of alternative fuels to date.

The user perspective reveals several potential reasons for the lack of acceptance. Among those may be the limited availability of fuelling station infrastructure and an overall lack of information and ignorance towards specific saving potentials. Ultimately, additional subsidisation measures, e.g. development of the fuelling station infrastructure along major motor- ways and through roads and improved information policy, may be required for the sustainable integration of LPG and CNG into road transport (see Chapter 4.2).

Page 18 of 79 3 Environmental comparison and potentials for renewable energies

The comparison of costs shows that the full costs of CNG and LPG vehicles are fully competitive with conventional engines while subject to energy tax benefits. Positive environmental effects associated with CNG and LPG are a prerequisite for an extended subsidisation through reduced energy taxes and additional measures (e.g. development of the infrastructure). A detailed environmental comparison considering present and future technologies is presented in the next chapter.

For this purpose, the overall procedure is introduced (3.1) followed by a detailed description of the baseline data on fuel supply (3.2) and vehicle operation (3.3). Chapters 3.4 and 3.5 illustrate and discuss the environmental impacts along the entire production pathway under present and future conditions.

3.1 Structure of the environmental comparison

The environmental comparison of CNG and LPG vehicles includes two separate time hori- zons, i.e. the present situation (2012) and a future scenario (2030). The vehicles, fuels and supply pathways under investigation are presented in detail in chapters 3.2 and 3.3.

Supply Time horizon Vehicle Fuel Emissions pathway

Passenger CO eq 2012 car LPG Crude oil 2

2030 City bus CNG Natural gas NMVOC

... …

Figure 4: Schematic of the environmental comparison

The environmental comparison is focused on GHG emissions. These are reported in CO2 equivalents. A brief explanation of the methodology for the calculation of CO2 equivalents associated with fuel supply may be found in Appendix II: Well-to-tank calculations. CO2 emissions derived from the combustion of fuels may be inferred from the carbon content and the heating values of the fuels. The fuel-specific emission factors reported in TREMOD [IFEU 2012] which are consistent with GHG inventories of the German Federal Environment Agen- cy (Table 1), serve as standard values for the calculations.

Page 19 of 79 Table 1: CO2 emissions from fuel combustion

Fuel Petrol Diesel CNG LPG g CO2 per MJ 72 74 56 65 Source: [IFEU 2012]

For fossil fuels, CO2 emissions derived from combustion during vehicle operation (TTW) are included. In contrast, vehicle operation with renewable fuels is considered carbon neutral. Therefore, only the proportion of fossil materials required for supply is factored in the calculations. GHG emissions from combustion of CH4 and N2O are always assigned to the TTW portion of the model. As a rule, these emissions account for an overall low percentage of the GHG emission total (see Chapter 3.3.3).

Parameters in addition to GHG emissions in the environmental comparison include:

Nitrogen oxides (NOX)

Non-methane hydrocarbons (NMHC)

Sulphur dioxide (SO2)

Renewable and non-renewable cumulative primary energy demand (CED)

The emission of the pollutants NOX, NMHC und SO2 contribute to air pollution in cities as well as acidification and eutrophication. Therefore, their annual emission rates are limited for each EU member state under the NEC Directive (2001/81/EC). At present, a future extension of the NEC Directive to include particulate matter emissions (in the form of PM2.5) is being discussed5. It was outside the scope of the present study to distinguish between fine and coarse particulates (dust) generated during fuel supply (WTT). Therefore, the investigation includes exhaust particles generated during vehicle operation (TTW) only (Chapter 3.3).

The cumulative energy demand (CED) is defined as the sum of all energies derived from primary energy feedstocks within the system, including renewable energies and nuclear energy. Nuclear energy in particular is associated with very low GHG emissions.

5 http://www.umweltbundesamt.de/luft/reinhaltestrategien/nec.htm

Page 20 of 79 3.2 Fuel supply – Well-to-tank (WTT)

Fuel supply is a central aspect of the environmental comparison due to the fact that fuel type and supply pathway may significantly influence the associated environmental impacts. The following chapter characterises the supply chains for CNG and LPG and the conventional fuels petrol and diesel. An analysis of the environmental impacts including the emissions of greenhouse gases (GHGs) and selected pollutants and energy consumption is carried out. However, the focus is on prospective renewable supply pathways and their potentials for the application in road transport.

3.2.1 Overview of the emission factors under investigation

Table 2 illustrates the overview of pathways included in the analysis with the respective energy consumption and associated emissions. For the characterisation of the current situation in 2012, a distinction was made between established (fossil only) and alternative fuel supply chains (LPG from natural gas and biomethane). For the projection of the year 2030, a number of fossil and renewable options were considered due to the fact that the political framework influencing the fuel mix in 2030 is not yet determined. From the present point of view, the supply chains under investigation are expected to be available in 2030.

A brief description of the individual pathways may be found in the following chapters. Addi- tional information on the methodology and assumptions for the calculation of well-to-tank emissions and energy consumption including detailed descriptions of the pathways or cross- references may be found in Appendix II: Well-to-tank calculations.

Page 21 of 79 Table 2: Overview of energy consumption and emissions WTT

Fuel Supply pathway Cumulative energy CO2 NMHC NOX SO2 CO2 demand (CED) eq eq WTW*

MJ/MJ % renew- g/MJ able

Typical pathways in 2012

Petrol Crude oil 1.176 0.1% 14.4 0.053 0.037 0.028 86.4

Diesel Crude oil 1.196 0.1% 16.0 0.025 0.040 0.031 90.0

LPG Crude oil 1.163 0.2% 13.8 0.134 0.050 0.089 78.8

CNG Natural gas 4000 km 1.209 0.9% 17.3 0.012 0.045 0.004 73.3

Alternative pathways in 2012

LPG Natural gas 1.118 0.1% 8.1 0.015 0.041 0.027 73.1

Biomethane6 Biogas / biodegradable 2.24 69.2% 29 0.005 0.030 0.024 29 waste (electricity mix today)

Biogas / renewable re- 2.99 79.6% 39 0.011 0.081 0.031 39 sources / liquid manure (electricity mix today)

Additional pathways for 2030

Petrol Tar sands 1.422 0.7% 29.6 0.111 0.069 0.149 101.6

Diesel Tar sands 1.445 0.7% 31.5 0.084 0.071 0.154 105.5

CNG/ bio- Natural gas 7000 km 1.255 1.1% 20.9 0.016 0.064 0.003 76.9 methane/ Biogas / biodegradable 1.9 86.8% 8.9 0.003 0.020 0.007 8.9 RE methane waste (electricity mix 2030)

Biogas / renewable re- 2.80 87.5% 26 0.010 0.074 0.020 26 sources / liquid manure (electricity mix 2030)

SNG / wood 2.20 87.3% 22 0.012 0.085 0.040 22 (electricity mix 2030)

Electricity / H2-Electrolysis 1.856 99.1% 1.6 0.003 0.002 0.001 1.6

NB: Blending of biofuels to fossil fuels not considered

*equals CO2 eq including CO2 from the complete combustion of fossil carbon. CH4 und N2O generated during combustion in the vehicle not included (see Chapter 3.3.3). Source: own calculations. See Appendix II: Well-to-tank calculations

6 CO2 eq in this study were updated from [BMVBS 2013]. The data are representative for the common range of the respective supply pathway.

Page 22 of 79 3.2.2 Comments on fossil fuel production and supply

At present, petrol and diesel are predominantly produced from crude oil. LPG in Germany arises as a byproduct during crude oil processing, although it may also be sourced as a byproduct during natural gas production. It is common practice to process LPG on site for subsequent transport to Europe by ship, whereas natural gas for CNG is commonly transported by pipeline (covering an average distance to the EU of 4000 km for marginal demand).

Future consideration of fossil fuel supply chains should seek to focus on demand and availability in particular. The average transport distance of natural gas for the supply of CNG is expected to rise to 7000 km by 2030. In addition to production from crude oil, petrol and diesel could be supplied through extraction from tar sands. At present, this technique plays a minor role in overall fuel consumption. However, the share of fuel derived from tar sands could increase in the future due to the scarcity of conventional crude oil. An increase in tar sand mining and processing would be associated with environmental impacts.

Blending of biofuels

It may be expected that fuels available at fuelling stations will contain a blend of biofuels, e.g.

- up to 7 vol. % biodiesel in diesel - up to 5 vol. % (E 5), or 10 vol.% bioethanol (E 10).

The stipulations of the Biofuels Quota (§ 37 BImSchG) of 6.25 % (MJ/MJ) further allow the offsetting of biomethane against the quota. Biofuels applied in the context of the quota achieved an energetic proportion of 5.6 % or 5.8 %7 in 2011 and 2012. In 2012, this would correspond to greenhouse gas (GHG) savings of approx. 2.9 % or 2.4 %, respectively, in reference to typical or default values of the 2009/28/EC Directive compared to purely fossil petrol or diesel.

Due to these minor GHG savings of biofuels, and the wide range of outcomes depending on substrate and country of origin of liquid biofuels, the focus of the present study is restricted to purely fossil fuel supply. For LPG derived from crude oil or CNG from natural gas, blending of biofuels (e.g. biomethane) is equally excluded.

3.2.3 Comments on renewable fuel production and supply

In principle, the individual drive options under investigation (diesel, petrol, CNG, LPG) are compatible with a multitude of fuels derived from renewable energy sources. One principal focus of the present study was the investigation of renewable fuels applicable to the target

7 Calculation based on [BLE 2013]

Page 23 of 79 drive options CNG/LPG, and the associated environmental impacts (see Table 2). In contrast, liquid biofuels are excluded from the present environmental comparison.

Renewable fuels for 2012 include compressed biomethane derived from biogas. In addition, the projection for 2030 explores biomethane produced from the gasification of wood chips with subsequent methanation (i.e. bio-SNG) and compressed methane derived from renewable electricity (RE methane). In theory, production of bio-LPG is equally conceivable, yet there is little market relevance at present. Therefore, this option is introduced, but not included in the environmental comparison scenario for 2030. In addition, liquefied biomethane (LBG – liquefied biogas) is currently under consideration in countries like Germany and the Netherlands, whereas Sweden and the United Kingdom are already establishing its application. However, due to the scarcity of data, this pathway is excluded from the analysis.

Table 3 gives a broad overview of the renewable fuels included in the analysis. A detailed characterisation may be found in the following paragraphs.

Table 3: Overview of the marketability of the renewable supply pathways under investigation

Pathway Brief description Feedstocks Technological Market situation status quo Biomethane Fermentation, gas Renewable resources Commercial GER: major capaci- from biogas processing (mostly maize) ties based on re- Organic waste and newable resources residues (esp. electricity and (e.g. biodegradable heat sector), minor waste, sludge, distill- capacities based on ers grains, straw) residues (currently relevant for the transport sector) Biomethane Gasification, gas condi- Lignocellulosic bio- Pilot phase EU: Demonstration from syn- tioning, synthesis, gas mass plant in thetic natu- processing Güssing/Austria, ral gas (Bio- commercial plants SNG) in Sweden under construction

RE- Electrolysis of H2 with Electricity, Pilot phase GER: ZSW/Stuttgart Methane renewable electricity (CO from air), CO2 2 and subsequent EWE/Werlte (CO2 methanation from biogas upgrading) Bio-LPG Byproduct of Oil-based (HVO) or HVO/HEFA: HVO: HVO/HEFA produc- lignocellulosic (BTL) commercial GER: no plant, tion; depending on the biomass BTL/FT: to date EU: Rotterdam, concept also pilot phase Porvoo BTL/Fischer-Tropsch- LPG utilisation Synthesis frequently plant- integrated (e.g. process energy)

Page 24 of 79 Biomethane

In 2010, approximately 10 PJ of gas fuels were utilised in Germany (Drucksache 17/9621 based on Energiestatistik). Biomethane may act as a supplement or substitute for natural gas, thus representing a strategic resource for sustainable mobility in the coming decades. Capacities for the supply of biomethane from biogas were substantially expanded in the past five years. However, the establishment of gas-powered vehicles has been relatively slow. As a result, biomethane sales targets in the fuel sector have been achieved to a limited extent.

The production of biogas via fermentation (anaerobic fermentation) with subsequent gas upgrading and infeed into the grid represents the current state of the art. The plant capacity installed by the end of 2012 of approx. 70,000 Nm3/h [DBFZ et al. 2013] equals an annual production capacity of more than 20 PJ. Moreover, further 36 plants are under construction, and 38 additional plants are in the planning stage [DENA 2013]. Throughout Europe, available capacities amount to approx. 700 MW of biomethane in the key regions Sweden, Switzer- land and the Netherlands [Green Gas Grids 2012]. More than 80 % of current facilities in Germany are operated with renewable resources, i.e. predominantly maize and grass-based silage, as well as animal waste like liquid manure. In the transport sector, biomethane is applied primarily from residues and waste materials. This may be linked to the fact that as of 2011, biomethane derived from residues and waste materials is eligible to receive double credits within the quota framework according to § 37 BImSchG. In contrast to bioethanol and biodiesel, there is no specific quota for biomethane. Moreover, natural gas as a fuel is not subject to a quota. As a result, biomethane is only applied to the quota as a biofuel if there is no alternative, or if available alternatives are cost-intensive in comparison.

Figure 5 presents biofuel utilisation in Germany in 2011 and 2012 according to an evaluation report8 of the German Federal Office for Agriculture and Food (BLE) in contrast with the offi- cial mineral oil statistics of the German Federal Office of Economics and Export Control (BAFA). According to [BLE 2013], approx. 0.3 PJ biomethane were applied in road transport, including one third not credited to the quota. In 2012, biomethane in road transport amounted to approx. 1.15 PJ, representing more than 10 % of natural gas based fuels. The total included 0.9 PJ (and 0.8 PJ thereof double credited) credited to the quota. The increase between 2011 and 2012 is based almost exclusively on biomethane from residues and waste materials. Please note that in contrast to the relative growth, the absolute increase of biodiesel derived from waste edible fats and oils is significantly higher than the increase of biomethane from residues and waste materials.

8 Applies to certified biomass after Biokraft-NachV and BioSt-NachV

Page 25 of 79 160 6.25% biofuels quota in 2012 equals approx. 136 PJ 140 Quota credit 136 PJ Quota volume 120 Tax-exempt biofuels

Biomethane double (waste) 100 Biodiesel double (waste)

80 Biomethane (esp. waste)

Biofuels Biofuels in PJ/a Bioethanol (energy crops) 60

Hydrotreated oils 40 Biodiesel (waste)

20 Biodiesel (oil seeds)

BLE data 0 2011 2011 2012 2012 BAFA data [BLE] [BAFA] [BLE] [BAFA]

Figure 5: Biofuels subject to energy tax benefits credited to the quota in 2011 and 2012 (DBFZ based on BLE 2013 and BAFA)

Sustainability certification is required for crediting9 to the biofuels quota. The German Bio- kraft-NachV10 does not define a default value for biomethane from renewable resources. Moreover, calculation methodology for the GHG balance complying with the legal framework is not fully developed to date.

Stakeholder projections for 2013 assume that the absolute volume of biomethane utilised in road transport will increase by a third in comparison with the previous year [DENA 2013]. Thus, the relative volume remains rather constant.

Verbio alone may supply biomethane from bioethanol production residues (distillers grains) with a current capacity of 60 MW11 to both the road transport and cogeneration sectors. Un- der the German Renewable Energy Act (EEG), biomethane from renewable resources is primarily applied in the electricity and heat sectors.

9 In this case by transfer of compliance with obligations to a third party according to § 37a Satz 4 BIm- SchG (German Federal Immission Control Act) 10 Biofuels Sustainability Ordinance 11 Source: verbiogas (http://www.verbio.de/fileadmin/user_upload/verbio/02_Produkte/FactSheet_verbiogas_PR.pdf), cor- responding to approx. 1.8 PJ/a at full load

Page 26 of 79 Furthermore, biomethane may be supplied through the gasification of lignocellulosic/ woody biomass with subsequent methanation. In contrast to biomethane from biogas, this conversion technology is not currently available on the market. Bio-SNG is successfully produced in a pilot plant in Güssing (Austria) with a capacity of 1 MW biomethane. Additional plants in the planning or construction stage are located in Sweden, Switzerland and Germany. However, expectations for development of bio-SNG production facilities fall short due to economic challenges in competitiveness, although the technology is readily available. Nevertheless, the production pathway remains promising for future utilisation of residues and waste materials as well as lignocellulosic biomass (no immediate food/feed competition).

Synthetic methane from renewable electricity (RE methane)

Electricity may be converted to hydrogen through electrolysis, which in turn may be used to synthesise methane in combination with CO2. The application of this procedure is being considered for wind and solar power plants at times of excess electricity and low demand. Thus, the integration of fluctuating renewable power sources into the energy system would be facili- tated [dena et al. 2012].

Excess electricity converted to RE methane may be stored in the existing natural gas infrastructure. Thus, storage of large capacities over extended periods of time is feasible, and the volumes in storage are available for a number of applications, including CNG fuel. However, future quantities of so-called excess electricity are very sensitive to a number of parameters. These include expansion of both the renewables sector and the grid, electricity storage, demand side management and not least increasing the flexibility of existing conventional power plants. Short-term gains from excess electricity are negligible compared to the total of electricity generated from renewable resources. Nonetheless, accelerated development of the renewable energy sector would in all likelihood result in regionally significant quantities within the present decade. Fluctuations in renewable electricity generation may reach proportions of 70 %, 80 % or more in the annual energy balance. If no countermeasures like energy storage are taken, the resulting excess electricity increases dramatically, as illustrated in Table 4 in scenario C 2023.

Table 4: ‘Dumped energy’ according to German Network Development Plan [NEP 2013, p. 64, Table 9]

Page 27 of 79 The simulations informing the German Network Development Plan show that the accelerated development of the renewables sector according to the energy plans of the German Federal States (NEP scenario C 2023) would significantly increase the proportion of renewable electricity lost to the grid (7.0 TWh in scenario C 2023, compared to 0 TWh and <0.1 TWh in the scenarios A 2023 and B 2023, respectively). This sensitivity is distinctly obvious in the comparison of the loss of 7.0 TWh of dumped energy under accelerated renewables development in the year 2023 (NEP scenario C 2023) with the loss of 0.8 TWh in 2023 under renewables development following the BMU Leitstudie (NEP scenario B 2023).

Even in the case that the quantities of so-called excess electricity could be contained with measures like grid expansion, electricity storage etc., the production of electricity-to-methane could accommodate relatively high technical potentials of renewable electricity in Germany. A strategic decision to produce RE methane with significant (renewable) energy input in order to utilise the product in combustion engines with relatively low energy conversion efficiency should be discussed in the context of various visions for mobility.

The production of hydrogen through water electrolysis could further develop into a relevant electricity consumer in the energy sector with significant potential to provide grid services, such as demand side management and demand response.

Figure 6 illustrates the underlying principles of the process electricity-to-methane (RE methane) exemplary for the utilisation of CO2 from biogas upgrading.

Figure 6: Methanation of H2 from electricity utilising CO2 from biogas upgrading

At the end of 2012, about 120 biomethane plants with an installed capacity of approx. 140,000 m³/h crude biogas, or an entry capacity of approx. 70,000 m³/h biomethane [DBFZ et. al. 2013], were in operation in Germany. The upgrading of biogas to natural gas quality entails the removal of CO2 with physico-chemical processes. The processing generally in-

Page 28 of 79 creases the methane content from 40 – 75 % in crude biogas to over 90 %. In compliance with § 36 of the Gas Grid Access Ordinance (Gasnetzzugangsverordnung - GasNZV), the resulting gas is required to comply with the stipulations in work sheets G 260 and G 262 of the German Association for Gas and Water e.V. (DVGW, Version 2007), both at the feed point and during the infeed. According to these stipulations, of the original CO2 content of 25

– 55 %, a maximum of 6 % may remain in the resulting biomethane. The arising CO2 may be utilised for the supply on synthetic methane. For a biomethane production of 560 Mio. m³/a12, a volume of approx. 300 Mio. Nm³/a CO2 is expected. In theory, these quantities could be utilised to produce approx. 3 TWh (10.8 PJ) of synthetic methane annually. The resulting methane is equal to the current consumption of natural gas in the transport sector, and corresponds to 0.46 % of the total fuel consumption in road transport in 2012. In theory, addition of CO2 extraction facilities to existing biogas production plants would be possible. Moreover,

CO2 may be extracted from air. Thus, the supply of CO2 does not present a major limitation for the production of RE methane. The energy demand according to Sterner [2009] amounts to approx. 8.2 MJ electricity per kg CO2, resulting in an additional electricity demand of approx. 0.45 MJ per MJ methane.

LPG from renewable feedstocks

The production of BTL (Biomass to liquid) fuels (HVO/HEFA) with hydrotreating of vegetable oil generates approx. 0.06 MJ gaseous products per MJ HVO according to the manufacturer [IFEU 2006]. For the most part, these products consist of LPG. An LPG content of energetic 5 % HVO of the total fuel consumption would result in a proportion of 0.35 % LPG from HVO production of the total fuel consumption.

The extent of market relevance remains to be seen. However, major market shares appear currently unlikely. Thus, the present study does not consider LPG from renewable feedstocks.

12 Capacity at the end of 2012 for 8,000 equivalent full load hours annually

Page 29 of 79 3.3 Vehicle operation – tank-to-wheel (TTW)

The operation of vehicles is associated with pollutants and GHG emissions generated during the combustion of fuels. There is a strong correlation between energy consumption and CO2 emissions on the one hand and the overall efficiency of the drive concept on the other (3.3.2). However, exhaust emissions are strongly dependent on the employed technologies for exhaust emission control, or the prevailing emission limits (3.3.3).

3.3.1 Vehicles under investigation

The vehicles included in the models were generic new vehicles of the medium size range per vehicle category according to TREMOD [IFEU 2012]:

Medium-size passenger car13

City bus (total weight 15-18 t) In this context, all possible drive concepts and fuel options were applied to a typical vehicle without further consideration of model-specific features. Thus, additional technological advances unrelated to engine or fuel type were excluded from the analysis.

Relevance of the vehicles included in the model

Passenger car transport is responsible for approx. 85 % of the mileage and 60 % of the GHG emissions in road transport [IFEU 2012]. In consequence, passenger cars were the focus of a number of recent studies comparing the drive concepts CNG and LPG (e.g. [JEC 2007], [DVFG 2010], [LBST 2010], [DENA 2011]). City buses, however, represent a special case of established CNG engines in the heavy commercial vehicle sector. Although buses do not feature strongly in the overall GHG balance, the air quality in inner city areas is strongly dependent on their emissions. Potentials may arise in this context for the overall integration of CNG into road transport through a dedicated development of the fuelling station infrastructure for fleets. Furthermore, the freight transport sector could benefit from the continued development of alternative engine technologies. A separate study in the context of the Mobility and Fuels Strategy investigated potentials of CNG and LNG (liquefied natural gas) for transport by lorry (see study on catenary hybrid trucks).

13 Defined as a passenger car with 1.4-2.0l engine displacement, according to TREMOD, representative of approx. 70 % of the vehicle sectors ‘lower middle class’ and ‘middle class’ registered with the Federal Motor Transport Authority.

Page 30 of 79 3.3.2 Fuel consumption

Due to the different specific CO2 emissions (per MJ) associated with CNG, LPG and conventional fuels (see Table 1 in 3.1), the energetic fuel consumption represents the most important factor in the comparison of GHG emissions. In this context, fuel consumption is strongly dependent on the individual features of the vehicle and the manner of operation, which should be representative across all engines in an environmental comparison. Con- sumption levels were derived from previous work carried out by the JEC group (JRC/Eucar/Concawe). Further data sources included the Manual for Emission Factors (HBEFA) and specific vehicle type-test data of recent vehicle models. The analysis and calculation of consumption levels is described in the following chapters.

Data sources and sensitivities

The difference between fuel consumption in CNG/LPG vehicles and petrol cars is dependent on a number of parameters. The energy conversion efficiency in the engine may be improved by the utilisation of fuels with a higher anti-knock capacity/ octane rating compared to petrol. The specific design of the vehicle plays a vital role and may differ significantly. The installation of LPG tanks and especially CNG tanks adds to the overall weight of the vehicle. Moreo- ver, engines of gas vehicles are frequently larger to compensate torque losses [JEC 2011]. Individual adaptations are ultimately part of the strategy of the individual manufacturer, however, they may influence fuel consumption significantly.

JEC 2011

The [JEC 2011]14 report took the adaptations described above into consideration for CNG vehicles, thus simulating comparable consumption levels aided by the ADVISOR model15 for the New European Driving Cycle (NEDC). However, for LPG vehicles, vehicle design was kept constant apart from a slight increase in the weight of the tank. The results of the model for new vehicles in 2002 were consistent with recent vehicle type-test data for new petrol cars.

The resulting consumption levels for present and future vehicle generations16 are presented in Table 5. According to JEC data, the fuel consumption of CNG and LPG of 187-190 MJ/100km in the generation ‘2010 advanced’ is comparable to petrol direct injection engines. Future concepts employing hybrid engine technology promise a significant improvement of

14 An update of the JEC report (Version 4, 2013) was carried out simultaneously to the present study, and could thus not be incorporated 15 A tool developed by the National Renewable Energy Laboratory (NREL) for the simulation of fuel consumption and driving quality (http://www.nrel.gov/vehiclesandfuels/vsa/related_links.html#advisor) 16 Defined as a generic ‘Golf class’

Page 31 of 79 efficiency. CNG hybrids are expected to specifically benefit due to the fact that their inherent efficiency advantage at high speeds is superior to petrol cars [JEC 2011]. Hybridisation of bivalent cars was not considered in the study, so data for the hybridisation of LPG remains unavailable.

Table 5: Fuel consumption of a small family car (Golf class) in the NEDC after JEC 2011

Petrol Diesel CNG LPG

Generation (Direct injec- (with particulate (Dedicated) (Bi-Fuel) tion) filter)

MJ/ MJ/ Diff. to MJ/ Diff. to MJ/ Diff. to

100km 100km petrol 100km petrol 100km petrol “2002 conventional“ 209 183 -12% 223 +7% 224 +7% “2010 advanced“ 188 166 -12% 187 -0,4% 190 +1% “2010 ad- 154 133 -14% 139 -10% n.a. vanced+hybrid“ Source: JEC 2011, data rounded to integers

Comparison with recent type-test data

In the following paragraph, type-test data for three recent vehicles of the manufacturer VW with LPG and CNG models are compared with data for new vehicle reported in the [JEC 2011] report. This serves the purpose of verification of assumptions and sensitivities on the parameters fuel consumption and vehicle design. The vehicles included for comparison are:

VW up 44 kW (petrol) with VW eco up 50 kW (CNG), VW Golf Plus 1.2 l TSI 77 kW (petrol) with Golf Plus 1.6 l BiFuel 75 kW (LPG), VW Caddy 1.2 l TSI (Petrol) with VW Caddy 2 l Erdgas (CNG) and 1.6 l BiFuel 75 kW (LPG)

The JEC vehicle is associated with lower CO2 emission both as a CNG or LPG engine compared to petrol models (Figure 7, top). ). A look at the three sample vehicles reveals that the

CNG and LPG engines showed CO2 emissions that were equal or higher compared to petrol cars. The reason for this may be the larger engine displacement, and the associated elevated consumption. In contrast, the VW Eco Up (CNG) was the only vehicle in which the engine displacement was held constant, and its CO2 emissions were reduced by 27 % compared to a petrol vehicle.

Page 32 of 79 +20% CO2 emissions per km (NEDC combined) +15% +10% +5% 0% +0% -5% CNG LPG CNG LPG CNG LPG -10% VW Up VW Golf VW Caddy JEC ("Golf class" -15% Plus 2010+) -20% -25% -30%

+80% Engine displacement +60% Engine power Vehicle weight +40%

+20%

+0% CNG LPG CNG LPG CNG LPG -20% VW Up VW Golf VW Caddy JEC ("Golf class" Plus 2010+)

Source: own calculations based on manufacturer data and [JEC 2011]

Figure 7: Exemplary comparison of CO2 emissions and relevant vehicle design of selected passenger cars

All gas-powered vehicles, especially CNG vehicles, carry additional weight in comparison with petrol models. However, at least in the case of the VW Eco Up (i.e. with a constant relative engine displacement) there are no negative impacts on CO2 emissions. All recent LPG models included in the analysis are fitted with a larger engine displacement, thus resulting in a higher weight and slightly higher CO2 emissions compared to the JEC model. The assumptions in the JEC report are primarily derived from converted LPG cars originally operated with petrol (see Chapter 2.2). In this case, drivers may be content to accept a certain loss of driving quality in the LPG mode and forego modification of the engine displacement if the petrol mode still delivers high performance. However, in this case the CO2 benefits of the LPG mode assumed in the [JEC 2011] report cease to apply.

In the present context, the analysis of type-test data may serve as an exemplary comparison. Beyond that, the interpretation of test-type data as representative and comparable levels of consumption is not valid due to the low number of models included, and the range of tech-

Page 33 of 79 nical modifications versus the petrol engine.

The JEC data, however, offer a consistent generic database for energetic consumption (in MJ). The applicability of the data is plausible under the assumed vehicle parameters.

Fuel consumption in TREMOD/HBEFA

In contrast to previous data sources, the HBEFA [INFRAS 2010] reports consumption for specific traffic conditions reflecting actual traffic. The TREMOD model ([FEU 2012] is also based on these data, thus allowing the weighting of specific traffic conditions and the calculation of consumption for typical segments of the German vehicle fleet. Consumption data for CNG and LPG cars is based on fewer actual measurements than petrol and diesel vehicles. For this reason, TREMOD/HBEFA data are not immediately applicable. They rather serve for the standardisation of consumption levels of the average German fleet of petrol and diesel vehicles in actual traffic. Furthermore, the consumption for new vehicle registrations in the years 2012 and 2030 may be inferred based on scenarios. For this purpose, TREMOD in- 17 cludes a trend scenario in which the CO2 fleet limit for passenger cars is reached in 2020 , and projected to decrease annually by 1.2 % from there.

Consumption levels for passenger cars

Table 6 illustrates the consumption derived for WTW comparisons for passenger cars in 2012 and 2030. Due to the fact that differences between the individual consumption rates of the “2010advanced” generation in the JEC 2011 report were non-significant, the same energetic fuel consumption is assumed for CNG/LPG and petrol cars for simplification.

Efficiency increases of the new vehicle fleet in 2030 for petrol and diesel engines correspond to the values of the TREMOD trend scenario (see above). This scenario reflects the likelihood of a (part) hybridisation. In a conservative approach, it is expected that half of the CNG new vehicle fleet will be at an advantage of 10 % relative to petrol hybrid vehicles according to [JEC 2011]. Thus, the overall fuel consumption of CNG vehicles in 2030 is projected to be 5 % lower compared to petrol cars. Due to the fact that there are no data available for LPG, the consumption is assumed to be equal to petrol cars.

17 The European average limit for passenger cars is 95 g CO2/km, the German level in TREMOD is at 108 g/km

Page 34 of 79 Table 6: Fuel consumption of average passenger cars in 2012 and 2030

TREMOD data Projected data in reference to JEC 2011 Petrol Diesel CNG LPG Generation MJ/ MJ/ MJ/ MJ/ Diff. to petrol Diff. to petrol Diff. to petrol 100km 100km 100km 100km 2012 238 198 -17% 238 - 238 - 2030 163 139 -15% 155 -5% 163 - Diff. to 2012 -32% -30% -35% -32% Source: TREMOD [IFEU 2012], own calculations based on [JEC 2011]

Consumption levels for city buses

City bus consumption (see Table 7) is calculated analogous to passenger cars. For diesel buses, the consumption is modelled as the average commercial vehicle in the German fleet for the years 2012 and 2030 in a typical inner-city traffic situation according to TREMOD/HBEFA.

In contrast to passenger cars, no type-test data is available for consumption of CNG city busses. However, based on recent data, the following assumptions may be made: the energetic consumption of a modern CNG bus with EEV standard according to HBEFA exceeds that of a diesel bus by 24 %, whereas [VTT 2012] quantifies the excess consumption between 32 % and 39 %. The discrepancy may be due to calculations based on differing inner- city driving cycles (VTT: ‘Braunschweig Cycle’ versus HBEFA: Weighting of specific inner- city traffic situations). For the environmental comparison in the present study, the excess consumption is simplified to an average of 30 % in 2012.

Similar to passenger cars, hybrid engines are assumed to be the key technology for city buses in 203018. Thus, the trend could equally apply to CNG buses. A number of sources ex- pect CNG engines to reap more benefits from increasing efficiency through hybridisation than diesel engines:

Spark-ignition engines utilising CNG or petrol are expected to benefit more strongly from hybridisation than compression-ignition engines such as diesel ([VTT 2012], [JEC 2011]).

CNG engines operated in the part-load range are less fuel-efficient, yet operation in this particular range is the rule in city traffic (JEC 2011). Thus, city buses are expected to benefit more strongly from hybridisation than passenger cars.

18 Since 2011, hybrids are the most common alternative drives among new registration motor buses [KBA 2011]

Page 35 of 79 Preliminary data for the Hyundai ‘Hybrid Blue-City’ report a 30-40 % decrease in consumption compared to non-hybrid CNG buses19. Thus, the results exceed the predic- tions of 20-30 % for diesel buses after [VTT 2012] by approx. 10 %.

Additional reductions in consumption for CNG city buses could be achieved through the dual-fuel technology that is currently being considered for commercial vehicles. With this approach, CNG may be employed in compression-ignition engines with a projected efficiency equal to diesel engines20.

Thus, the scenario for 2030 assumes a relative decrease of consumption of 20 % for diesel and 35 % for CNG city buses, resulting in a reduction of the excess consumption of CNG buses to 5 %.

Table 7: Fuel consumption of average city buses in 2012 and 2030

Diesel CNG Generation MJ/100km MJ/100km Diff. to diesel 2012 1210 1573 +30% 2030 970 1022 +5% Diff. to 2012 -20% -35% Source: TREMOD [IFEU 2012], [VTT 2012], own assumptions

3.3.3 Greenhouse gas and pollutant emissions

In addition to CO2, vehicles with combustion engines emit GHGs in the form of CH4 (methane) und N2O (nitrous oxide). In contrast to the linear correlation between CO2 emissions and fuel consumption, the emissions of methane, nitrous oxide and other air pollutants are influenced by engine technology and exhaust gas aftertreatment measures. The Handbook ‘Emission Factors for Road Transport’ (HBEFA) supplied data for modelling based on actual typical traffic conditions. Thus, in addition to distinction according to vehicle type and fuel type, the factors road category and exhaust technology may be included. Assignments were made for the following emission factors:

Passenger car:

Average distribution of mileage in all road categories

Exhaust emission standard Euro 5 for 2012, Euro 6 for 2030

Fitting of diesel cars with particulate filters

19 http://www.hyundai.com.au/About-Hyundai/News/Articles/Hyundai-continues-its-Blue-Drive-push- with-CNG-Hybrid-Bus/default.aspx 20 http://cleanairpower.com/duel-technology.php

Page 36 of 79 City bus

Mileage in inner city areas only

Exhaust emission standard diesel: Euro V incl. exhaust gas recirculation for 2012, EURO VI for 2030

Exhaust emission standard CNG: EEV (Enhanced Environmentally Friendly Vehicle)

Table 8 illustrates the GHG emissions factors under investigation. GHG emissions generated during vehicle operation are highest for petrol vehicles and lowest for CNG. The GHG advantage of CNG and LPG is mainly based on the low carbon content. The advantage of diesel, however, is related to the higher energy efficiency of the engine. For this reason, the GHG emissions of CNG city busses with lower efficiency in 2012 are marginally lower than those of the diesel buses. In 2030, however, increased efficiency of CNG engines is expected to result in a pronounced GHG advantage. The GHGs N2O and CH4 account for a minor proportion of the GHG emission total (max. 2.6 %).

Table 8: Emission factors for greenhouse gases TTW

CO2 equivalents N2O CH4 Vehicle/ Engine Diff. to petrol car/ part Emission Standard g/km mg/km mg/km Diesel bus N2O+CH4 Petrol - 0.2% 172 0.4 7

Passenger car 2012 CNG -22% 0.3% 134 0 15 (Euro 5) LPG -9% 0.6% 156 2.0 15 Diesel -14% 1.1% 148 4.7 10 Petrol - 0.2% 118 0.4 6

Passenger car 2030 CNG -26% 0.4% 87 0 13 (Euro 6) LPG -9% 0.9% 107 2.0 13 Diesel -11% 1.5% 104 4.7 9

Bus 2012 Diesel 0.2% 895 0 77 (Euro V) CNG 0% 1.7% 881 0 623

Bus 2030 Diesel 0.1% 718 0 35 (Euro VI) CNG -18% 2.6% 572 0 623 Source: Own calculations. HBEFA 3.1

The resulting differences between actual air pollutant emissions of the engines under investigation are slight according to HBEFA. As a rule, the emission limits according to Euro 5/V and Euro 6/VI are complied with under actual traffic conditions. An exception may be found in

LPG and diesel cars with NOX emissions that exceed emission limits derived from test cycles in actual traffic conditions. For the 2030 scenario, this assumption of the HBEFA has not

Page 37 of 79 been adopted. Compliance with the limit under actual traffic conditions in 2030 is anticipated instead.

The emission performance of CNG buses with respect to PM emissions is superior to Euro V diesel buses. However, the introduction of the Euro VI standard will render these differences negligible. It is expected that the associated requirements for exhaust gas aftertreatment technologies, e.g. SCR and particulate filter systems, will result in additional costs and the need for more sophisticated maintenance and monitoring measures. CNG buses will be exempt from these requirements.

Table 9: Emission factors for air pollutants TTW

Vehicle/ NOx PM NMHC CO SO2* Engine Emission Standard g/km mg/km mg/km g/km mg/km Petrol 6.8 0.56 0.87 0.06 Passenger car 2012 CNG 1.9 1.2 0.48 0 (Euro 5) LPG 0.1 11.5 0.90 Diesel 0.53 1.5 9.5 0.02 0.74 Petrol 5.9 0.44 0.60 0.05 Passenger car 2030 CNG 1.6 1.0 0.38 0 (Euro 6) LPG 0.08** 9.9 0.71 Diesel 0.06** 1.4 8.5 0.03 0.52

Bus 2012 Diesel 3.37 44.8 74.8 1.03 0 (Euro VI/EEV) CNG 0.83 1.5 49.8 1.18 4.51

Bus 2030 Diesel 0.62 5.5 33.9 1.32 0 (Euro VI/EEV) CNG 0.83 1.5 49.8 1.18 3.61 * based on a sulphur content of 8 ppm for petrol/diesel ** in contrast with HBEFA, compliance with the limit is assumed Source: HBEFA 3.1. Own calculations

Research on converted LPG engines in Euro 4 passenger cars showed that emissions may in some cases rise significantly compared to the original petrol vehicle [EMEP/EEA 2012]. These results could not be verified in the following environmental comparison for present and future commercial vehicles. However, the findings should be incorporated in the evaluation of present LPG passenger cars, as the majority of the present LPG fleet has undergone conversion.

Page 38 of 79 3.4 Well-to-wheel (WTW) comparison 2012

3.4.1 Greenhouse gas emissions

Passenger car

Given the present fuel supply pathways, the comparison of GHG savings in reference to a petrol engine shows that CNG cars generate the highest GHG savings with 15 %, followed by diesel with 13 % and LPG with 9 % (Figure 8). ). The differences illustrate the relevant GHG savings potentials of the individual fossil fuels for a generic average passenger car. However, the considerable range associated with individual car models should be kept in mind (see Chapter 3.3.2). Yet, significantly higher GHG savings may be achieved with renewable fuels. The GHG emissions of CNG vehicles operated with biomethane produced from biodegradable waste are 66 % lower compared to a petrol vehicle. The utilisation of biomethane derived from renewable resources/ liquid manure WTW may save 55 % of GHG emissions.

WTW Greenhouse gas emissions for passenger cars in 2012

WTT TTW In g CO2 eq / km 200 -13% -9% -15% -15% -66% -55%

150

100

Biomethane – renewable 50 resources / Biomethane – liquid biodegradable Natural gas manure* Crude oil (4000 km) waste* Crude oil Crude oil Natural gas 0 Petrol car Diesel car LPG car CNG car LPG car CNG car CNG car Established pathways Alternative pathways *Update on biomethane [BMVBS 2013] (see Chapter 3.2)

Figure 8: WTW Greenhouse gas emissions for passenger cars in 2012

Page 39 of 79 Comparison with other studies

Recent work on the comparison of LPG and CNG vehicles employ a range of methods and show considerable variation in the input data. Thus, findings may significantly differ between studies. In the following, the underlying assumptions and methodology of the present study are compared to the study of the German LPG Association [DVFG 2012] and the study of the Association Erdgas Mobil [LBST 2010].

Distinctions between the studies

The study of the German LPG Association investigates CNG, LPG and petrol vehicles. In contrast to the present study and [LBST 2010], renewable fuel supply pathways are not con- 21 sidered. Therefore, only CO2 emissions of recent passenger cars operated with fuels produced from fossil supply pathways are included. Moreover, only the status quo is presented, as the [DVFG 2012] study does not include future scenarios.

Table 10: System boundaries and fundamental assumptions of recent studies on environmental comparisons of CNG/LPG with other fuels

Study [DVFG 2012] [LBST 2010] Present Study Location WTT: EU EU Germany TTW: Germany Period of Status quo (2010) 2010 2012 investigation 2020 2030 Vehicle type Passenger car Passenger car Passenger car (Qualitative assessment Bus of commercial vehicles) WTT Specific pathways Ranges Specific pathways Renewable energies ex- Renewable energies Renewable energies excluded examined (CNG) amined (CNG) TTW Variety of vehicles (Stock Generic vehicle “Golf Generic vehicle (car 1.4-2l Germany according to class” engine displacement). DAT). Ranges Means Means (cohorts)22

21 CO2 equivalents from CH4 and N2O are excluded from the model, thus the comparison is based on CO2 only. This is a valid simplification due to the low proportion of CH4 and N2O (see Chapter 3.3.3) 22 Calculation of TTW GHG savings in Table 7, line 4 in DVFG 2012 inexplicable

Page 40 of 79 Results WTW, WTT and TTW

Figure 9 illustrates the differing results for CO2 emissions of CNG and LPG cars. Thus,

[DVFG 2012] finds that the CO2 emissions per km of an LPG car are 4 % lower than those of a CNG car across the entire causal chain (WTW). However, both the present study and [LBST 2010] report higher GHG savings for CNG (-7 % and -16 %, respectively).

g CO2/km LPG CNG This study Crude oil -20% 4000km WTT DVFG 2012 Natural gas -45% 4000km LBST 2010 Crude oil -32% 1000km g CO2/km - TTW -200 -100 0 100 200 LPG CNG This study Equal engine efficiency -14% TTW DVFG 2012 LPG more energy-efficient -6% LBST 2010 Similar engine efficiency -13% g CO2/km - WTW -200 -100 0 100 200 LPG CNG This study -7% WTW DVFG 2012 -4% LBST 2010 -16%

-200 -100 0 100 200

Figure 9: Comparison of the CO2 benefits of CNG and LPG from fossil supply pathways for motors cars in 2010/2012 in recent studies

The reasons for the discrepancies may be explained with differences in the underlying assumptions for WTT and TTW.

Analogous across all studies, the CO2 parameters for fuel supply (WTT) are based on data reported in the JEC studies [JEC 2011]. However, differing assumptions for the origin of fossil fuels in Germany were made:

[DVFG 2012]: LPG from natural gas (transport by ship). CNG per pipeline, distance 4000 km

[LBST 2010]: LPG from crude oil. CNG from the North Sea, distance 1000 km

Present Study: LPG from crude oil. CNG per pipeline, distance 4000 km

The resulting differences between the supply pathways are considerable, and may result in favourable CO2 emissions for LPG (DVFG and present study) or CNG (LBST) depending on the assumptions.

In the present study, the fuel supply was specifically adapted to the status quo in Germany.

Page 41 of 79 Thus, the present results and the reported CO2 emission advantage of -20 % for LPG are likely to be plausible. However, the influence of the (fossil) fuel supply on WTW emissions was revealed to be minor (below 50 g CO2/km).

In contrast, the influence of the assumptions concerning fuel consumption, or rather the GHG emissions generated during vehicle operation (TTW), is highly significant. The present study and the Erdgas Mobil study are based on JEC data [JEC 2011]. Thus, the underlying assumptions for CNG, LPG and petrol were similar, revealing a CO2 advantage of CNG over

LPG between -13 % and -14 % (Figure 9). In contrast, DVFG (2010) inferred average CO2 savings from a number of type-test data, resulting in CO2 savings of only -4 % for CNG compared to LPG. In this case, the energetic fuel consumption in LPG vehicles would be approx. 11 % lower than in CNG vehicles (and approx. 4 % lower than in petrol cars). The caveats of type-test data for generalised calculations have been introduced in Chapter 3.3.2. Test-type data may be useful to illustrate ranges and sensitivities. However, simple calculation of the mean will not ensure the delivery of consistent consumption rates for similar vehicles.

Conclusions

The CO2 emissions of CNG and LPG passenger cars are strongly dependent on underlying assumptions. The most significant factor is the vehicle fuel consumption (TTW). As a rule,

CO2 emissions of CNG compare favourably due to the low overall carbon content. Even the most favourable assumptions for LPG regarding fuel supply and consumption will not fully close the gap in the CO2 advantage of CNG over LPG. Moreover, it is essential for the assessment of environmental benefits of CNG and LPG to include renewable fuel supply pathways. A comparison of supply from solely fossil feedstocks is thus incomplete.

Page 42 of 79 City bus

The GHG emissions of a city bus are illustrated in Figure 10. Due to the significantly elevated energetic fuel consumption of CNG buses, the GHG emissions of a CNG bus operated with natural gas are even higher than those of a diesel bus. However, the actual difference of 7 % is relatively minor. Moreover, the application of biomethane may decrease GHG emissions significantly in comparison with purely fossil diesel (42 % reduction for renewable resources/ liquid manure, 57 % for biodegradable waste). As an alternative to CNG, biodiesel may be utilised. However, in this case disadvantages resulting from pollutant emissions similar to those of conventional diesel may be expected (see following chapter).

WTW greenhouse gas emissions of city buses in 2012 1400 In g CO2 eq / km WTT TTW 1200 +7%

1000 -57% -42%

800

600 Biomethane – 400 renewable Biomethane - resources / 200 biodegradable liquid manure Natural gas waste Crude oil (4000km) 0 Diesel bus CNG bus CNG bus CNG bus

Established pathways Alternative pathways

Figure 10: WTW greenhouse gas emissions of city buses in 2012

Page 43 of 79 3.4.2 Primary energy consumption and pollutant emissions

Passenger car

Figure 11 reveals that diesel cars are associated with the lowest primary energy consumption relative to established fuel supply pathways. The range between petrol, LPG and CNG (approx. 4 %) is smaller compared to that of the GHG emissions. The primary energy consumption of CNG based on biomethane is considerably higher than that of the fossil pathways. However, the high consumption is offset by the fact that the consumption of fossil (non-renewable) energies is low.

Primary energy consumption NOX 8 0.7 In MJ/km Renewable In g/km 7 0.6 TTW Non-renewable 6 0.5 WTT 5 4 0.4 3 0.3 2 0.2 1 0.1 0

–

crude oil

crude oilcrude

–

natural gas natural

–

natural gas natural gas natural

–

LPG

Petrol Petrol

Diesel Diesel

LPG

Biomethane Biomethane

CNG CNG

Petrol Petrol

Diesel Diesel

LPG

Biomethane Biomethane

CNG CNG

renewable renewable resources

biodegradable biodegradable waste renewable renewable resources biodegradable waste

NMHC SO2 0.35 0.25 In g/km TTW 0.30 In g/km TTW 0.20 0.25 WTT WTT 0.20 0.15 0.15 0.10 0.10 0.05 0.05

0.00 0.00

–

crude oilcrude

crude oil crude

crude oilcrude oilcrude

crude oil crude crude oilcrude

– –

–

natural gas natural natural gas gas natural

natural natural gas

– –

LPG

Petrol Petrol

Diesel Diesel

LPG

Biomethane Biomethane

CNG CNG CNG

renewable renewable resources

renewable renewable resources biodegradable biodegradable waste biodegradable waste Source: HBEFA 3.1. own assumptions and calculations Figure 11: WTW pollutant emissions of passenger cars in 2012

The emissions of the pollutants NMHC and SO2 are generated primarily during fuel supply (WTT). These are highest for LPG as a byproduct of crude oil processing. Page 44 of 79 NOx emissions in significant quantities arise during operation (TTW). These are highest for diesel vehicles compared to the alternatives available. For air quality control purposes, the substitution of diesel cars with CNG promises several benefits, as CNG cars are associated with GHG savings in addition to lower NOx emissions. Substitution with LPG, however, is disadvantageous with respect to NMHC and SO2 emissions. Moreover, converted vehicles could generate additional actual emissions compared to petrol cars (see Chapter 3.3.3).

Page 45 of 79 City bus

Diesel buses are associated with the lowest total primary energy consumption. The result reflects the low energetic fuel consumption of diesel buses compared to CNG (Figure 12). Operation with biomethane also requires a primary energy consumption significantly exceeding that of fossil fuels. Yet, the quantities of fossil energy consumed are much lower.

The principal advantage of a CNG-powered city bus lies in the low actual pollutant emissions

(TTW) of NOX (also PM, see Chapter 3.3.3) which are beneficial to local air quality. From the WTW perspective, pollutant emissions are also lower for biomethane compared to diesel buses with the exception of SO2.

Primary energy consumption NOX 50 5 In MJ/km In g pro km TTW 40 4 WTT 30 3 Renewable 20 Non-renewable 2 10 1

0 0

–

crude oil crude

crude oilcrude

–

natural gas natural

–

Diesel Diesel

Biomethane Biomethane

Diesel Diesel

CNG CNG

Biomethane Biomethane

CNG CNG

renewable renewable resources

biodegradable biodegradable waste renewable resources renewable waste biodegradable

NMHC SO2 0.4 0.6 In g/km In g/km TTW TTW 0.5 WTT 0.3 WTT 0.4 0.2 0.3 0.2 0.1 0.1

0 0

–

crude oilcrude

–

natural gas natural

–

Diesel Diesel

Biomethane Biomethane

Diesel Diesel

CNG CNG

Biomethane Biomethane

Biomethane

CNG CNG

renewable resources renewable

biodegradable biodegradable waste renewable resources renewable biodegradable biodegradable waste Source: HBEFA 3.1. own assumptions and calculations

Figure 12: WTW pollutant emissions for city buses in 2012

Page 46 of 79 3.5 Well-to-wheel (WTW) comparison 2030

3.5.1 Greenhouse gas emissions

Passenger car

The scenario 2030 assumes significant reductions in fuel consumption for all vehicles (-30 % to -35 % MJ/MJ). As a consequence, GHG emissions for all included alternatives decrease considerably. For instance, emission from a petrol vehicle operated with crude oil-derived fuel are projected to fall from 206 g CO2 eq/km in 2012 to 141 g CO2 eq/km in 2030 (Figure 8, Figure 13). For the established fossil fuel supply pathways, the relative changes in GHG emission rates between 2012 and 2030 in reference to petrol cars are minor. For CNG cars, the ratio of GHG emissions is slightly shifted towards the fuel supply stage (WTT) due to the longer transport distance (7000 km instead of 4000 km). However, the shift is compensated by the additional reduction in consumption associated with CNG hybrid vehicles. GHG savings of CNG cars versus petrol cars remain constant at 15 %.

WTW greenhouse gas emissions for passenger cars in 2030

180 In g CO2 eq/ km WTT TTW 160 Additional WTT proportion for extraction from tar sands 140 -9% -15% -15% -90% -76% -98% 120

100

80 Biomethane/ SNG – wood 60 Biomethane - biodegradable 40 waste RE-Methane- 20 Natural gas wind energy Crude oil Crude oil Crude oil (7000 km) Natural gas 0 Petrol Diesel LPG car CNG car (Natural gas/methane) car car

Figure 13: WTW greenhouse gas emissions for passenger cars in 2030

A key topic for future evaluations will be the shift of fuel supply pathways. In the event that the enormous demand for petrol and diesel fuel cannot be met with crude oil anymore, other sources such as tar sands may be exploited for fuel supply. In consequence, the GHG balance of these fuels would deteriorate (for petrol from 141 g/CO2 eq/km to 166 g/CO2 eq/km). For LPG, the consequences are harder to predict. In the case that LPG was produced from

Page 47 of 79 fossil natural gas deposits like CNG, the GHG emission would remain constant. In fact, the GHG advantage compared to petrol and diesel would grow more pronounced.

For CNG vehicles, renewable resources would continue to be available in 2030. Biomethane (from biogas produced from waste or bio-SNG) and RE methane derived from wind energy electrolysis could potentially achieve GHG savings between 76 % and 98 %. The supply of biomethane from biodegradable waste is associated with significantly lower GHG emissions compared to 2012.

City bus

Heavy commercial vehicles such as city buses could also benefit from CNG engines for future GHG emissions savings compared to diesel-powered vehicles. These savings are associated with efficiency increases of the vehicle (TTW), e.g. hybrid or dual-fuel engines. These advanced technologies would close the gap in consumption efficiency between diesel and CNG. In addition, a shift in fuel supply pathways towards renewable methane or diesel from tar sands could result in GHG benefits for CNG buses (Figure 14).

WTW greenhouse gas emissions of city buses in 2030 1200 In g CO2 eq/ km WTT TTW Additional WTT proportion for 1000 extraction from tar sands

800 -8% -88% -74% -98%

600

Biomethane/ 400 Biomethane - SNG – wood biodegradable 200 waste RE-Methane- Natural gas wind energy Crude oil (7000km) 0 Diesel bus CNG bus (Natural gas/methane)

Figure 14: WTW greenhouse gas emissions for city buses 2030

Page 48 of 79 3.5.2 Primary energy consumption and pollutant emission

Passenger car

In analogy to GHG emissions, primary energy consumption and WTW pollutant emissions are expected to decrease significantly in absolute terms with improved efficiency in reference to 2012 (Figure 15). In this context, the primary energy demand of biomethane and RE methane may be met with 80 % to 100 % renewable energies.

Primary energy consumption NOX 5 0.30 In MJ/km In g/km WTT (Tar sand) 4 0.25 TTW 0.20 WTT 3 Renewable 0.15 2 Non-renewable 0.10 1 0.05

0 0.00

–

crude oilcrude

crude oil

crude oilcrude

–

natural gas gas natural

electricity

natural gas natural

electricity

SNG - wood - SNG

– –

SNG - wood - SNG

Biomethane/

RE-Methane-

–

Biomethane/

RE-Methane-

LPG

Petrol

Diesel Diesel

LPG

Biomethane Biomethane

Petrol Petrol

Diesel Diesel

LPG

CNG CNG

Biomethane Biomethane

CNG CNG biodegradable biodegradable waste biodegradable waste

NMHC SO2 0.25 0.30 In g/km In g/km WTT (Tar sand) WTT (Tar sand) 0.20 0.25 TTW TTW 0.20 0.15 WTT WTT 0.15 0.10 0.10 0.05 0.05

0.00 0.00

–

crude oilcrude

crude oil crude

crude oilcrude

crude oil crude

–

natural gas natural gas natural

–

electricity

natural gas natural

electricity

SNG - wood - SNG

– –

Biomethane/

RE-Methane-

SNG - wood - SNG

–

Biomethane/

RE-Methane-

LPG

Petrol Petrol

Diesel Diesel

LPG

Biomethane Biomethane

CNG CNG

Petrol Petrol

Diesel Diesel

LPG

Biomethane Biomethane

CNG CNG biodegradable biodegradable waste biodegradable waste Source: HBEFA 3.1. own assumptions and calculations Figure 15: WTW pollutant emissions for passenger cars 2030

NOx emissions continue to arise in relevant quantities TTW. However, compliance with the Euro 6 standards considerably reduces differences between the individual fuel types. The

WTT angle reveals significant differences between the fuel supply pathways. The NOx emissions of LPG and CNG (with the exception of RE methane) exceed those of petrol and diesel Page 49 of 79 from crude oil, yet the NMHC and SO2 emissions of CNG tend to be lower, particularly in comparison to petrol and diesel extracted from tar sands. In line with GHG emission results, the most favourable overall pollutant balance may be observed for CNG passenger cars operated with RE methane from renewable electricity sources.

Page 50 of 79 City bus

Reduced consumption levels of both CNG and diesel buses are going to decrease future primary energy demand. Moreover, a considerable drop is expected in the demand for fossil energy for renewable methane versus diesel from crude oil compared to 2012 (Figure 16). Primary energy consumption NOX 35 2.00 In g/km 30 In MJ/km Renewable Non-renewable 25 1.50 WTT (Tar sand) 20 TTW 1.00 WTT 15 10 0.50 5

0 0.00

–

electricity

SNG - wood - SNG

Diesel-Rohöl

Biomethane/

RE-Methane-

Biomethane/

RE-Methane-

CNG-Natural gas CNG-Natural

Biomethane Biomethane

Biomethane Biomethane biodegradable biodegradable waste biodegradable biodegradable waste

NMHC SO2 0.7 1.80 In g/km WTT (Tar sand) In g/km 0.6 1.50 WTT (Tar sand) TTW TTW 0.5 1.20 0.4 WTT WTT 0.90 0.3 0.2 0.60 0.1 0.30

0.0 0.00

–

electricity

SNG - wood - SNG

Diesel-Rohöl

Biomethane/

RE-Methane-

Biomethane/

RE-Methane-

CNG-Naturalgas

CNG-Natural gas CNG-Natural

Biomethane Biomethane

Biomethane Biomethane biodegradable biodegradable waste biodegradable biodegradable waste Source: HBEFA 3.1. own assumptions and calculations Figure 16: WTW pollutant emissions for city buses in 2030

The differences in actual pollutant emissions (TTW) of CNG and diesel are negligible after introduction of the Euro VI standard. However, diesel engines may be subject to additional exhaust gas aftertreatment measures associated with additional costs. For pollutant emissions generated during fuel supply (WTT), a picture similar to the passenger car scenario emerges, i.e. the lowest emissions are associated with RE methane. In the case of biomethane, NOX and SO2 emissions may exceed those of diesel produced from crude oil. However, low to no additional pollutant emissions are associated with the operation of CNG buses, particularly if future diesel fuel will be extracted from tar sands.

Page 51 of 79 4 Perspectives for the promotion of CNG and LPG in road transport

4.1 Benefits from an environmental perspective

Both CNG and LPG offer advantages over crude oil-based petrol and diesel fuels. Although (actual) pollutant emissions are similar to petrol engines, both CNG and LPG show a more favourable GHG balance. Due to the fact that climate change mitigation represents one of the major political challenges, a favourable GHG balance may be well received in support of an extension of subsidies.

However, a comparison of CNG/LPG and petrol from fossil supply pathways23 reveals the limited cost efficiency of relative GHG savings in correlation with financial losses associated with energy tax benefits (see Figure 17). Due to moderate GHG savings of -9 % to -15 %, diesel is currently the most cost-efficient fuel apart from pure biomethane. In addition, energy tax losses for diesel are largely compensated with an overall higher motor vehicle tax. In the cases of fossil CNG, and LPG derived from crude oil in particular, subsidisation with energy tax benefits may not be justified with GHG savings or superior cost efficiency (in this context, rebound effects, such as improved mileage through lower costs, are not taken into consideration).

Energy tax losses in EUR per ton CO2 savings 0 500 1000 1500 2000 2500 0%

LPG 10% Diesel* CNG 20%

30%

40%

50% Relative GHG savings per vehicle km vehicle per savings GHG Relative 60% CNG - 100% Biomethane (from biodegradable waste) 70% *increased motor vehicle tax rate not considered

Figure 17: Energy tax losses and GHG savings in relation to a petrol vehicle in 2012 (Calculation in Appendix III)

23 Blending of biofuels not considered

Page 52 of 79 In addition to the relative GHG savings, a number of arguments in favour of a strategic subsidy extension of CNG or LPG exist. The scope of the present study is limited to a qualitative assessment of these factors:

Diversification of fuels – crude oil-independent fuels should be promoted to ensure security of supply. Both CNG and LPG qualify when derived from natural gas.

Integration of renewable energies – the road transport sector should seek to utilise renewable energies in the long-term. At present, there are perspectives for CNG but not for LPG.

Thus, LPG has a strategic potential to contribute to diversification only, whereas CNG is may be expected to also facilitate the integration of renewable energies and future technologies into road transport.

The distribution of CNG and the associated development of the required infrastructure may further offer opportunities to exploit additional potentials for the diversification of fuels and integration of renewable energies in the commercial vehicle sector. For instance, the CNG infrastructure could be instrumental in the establishment of renewable methane not only in the car sector, but also in additional areas (e.g. LNG for long-distance freight transport).

4.2 Potential subsidy framework

From an environmental perspective, the application of CNG is more profitable than LPG. This should be taken into account during the design of an extension of current energy tax benefits. Renewable supply pathways should be the particular focus of the extension. Alternative applications of biomethane may be restricted to small-scale utilisation schemes (cogeneration applications), or they may be associated with significantly reduced GHG savings (heat applications). Therefore, available biofuels should be promoted to find broad application in the near future, including utilisation in road transport. Support to this scheme could come from an additional, or exclusive, subsidy of renewable methane through energy taxation as a prerequisite for tax benefits. Further, statutory quotas assigning renewable methane for utilisation as CNG fuel could be defined.

LPG is associated with fewer environmental benefits at present, and projected to hold less potential for the reduction of environmental burdens. Moreover, the implementation of renewable LPG components appears unlikely given the present development trajectory. These facts should be considered in the debate over an extension of subsidisation. However, the contribution of LPG to the diversification of the fuel market should be given proper regard.

As an alternative to the present energy tax benefits, subsidies in Germany could be modelled on the EU alternative fuels strategy. In this case, energy taxation would follow the emissions of CO2 or GHGs per MJ fuel. A specific distinction of the existing fuels and the respective

Page 53 of 79 supply pathways would thus allow accounting for the differences in GHG emissions for CNG and LPG from fossil and renewable pathways.

However, the low overall integration of new CNG and LPG vehicles to date indicates that measures beyond benefits in energy taxation may be required. These measures should include aspects such as the development of the fuelling station infrastructure (for CNG in particular) and detailed consumer information, thus addressing multiple stakeholders. In this context, the ‘Initiative Natural Gas Mobility – CNG and Biomethane fuels’ should be noted as a source of information. The initiative was coordinated by the dena with support of the BMVBS, and targeted the development of measures in collaboration with key players in the energy industry and the road transport sector (see http://www.erdgasmobilitaet.info).

Table 11: Supporting framework for the subsidisation of CNG and LPG

CNG LPG Extension of the reduced energy tax. distinction be- No extension. or adapted rate of the reduced tween fossil and renewable CNG/methane as appro- energy tax priate Blending quotas for renewable methane GHG=based energy tax following EU alternative fuels strategy Development of service station infrastructure dependent on demand Revision and update of consumer information regarding fuel pricing and service station labelling Expanded supply and improved communication on new motor vehicles on the market

Page 54 of 79 Appendix I: Amortisation potential of LPG conversion for the Ger- man petrol vehicle fleet

Figure 18 illustrates the potential of an LPG conversion for the German petrol vehicle stock. The vehicles in stock were assigned model-specific individual mileages based on empirical data after [MiD 2008] and [Polk 2008]. Calculations were carried out considering consumption and annual mileage. The individual conversion costs depend on the specific engine (characterised by engine displacement, year of manufacture and exhaust emission standard) with a discounting of 2 %. The assumed maximum mileage to end-of-life of the vehicle is 200,000 km. Vehicles include models built from 1995.

Figure 18: Potential of conversion to LPG for the German vehicle fleet

Thus, 20 % of the German vehicle will redeem conversion expenses within two years, assuming current operation levels and tax benefits. Without tax benefits, only 10 % of the fleet will break even within two years of conversion. Amortisation is most readily achieved for vehicles with high mileage or fuel-intensive cars with simple engines (and inexpensive conversion). The figure illustrates the immense potential for cost reduction through LPG conversion in the actual fleet. For the majority of the fleet, it is evident that conversion costs are re- deemed within a few years. Despite the obvious benefit, an annual percentage of only 0.3 % of the fleet is actually converted from petrol to LPG.

In the case of a short period of ownership, conversion may still break even due to a higher resale value of the vehicle. In this case, the added value is transferred to the next owner through the residual value. Page 55 of 79 Appendix II: Well-to-tank calculations

Methodology

Well-to-tank calculations were carried out according to established LCA standards, i.e. ISO 14040 and ISO 14044.

Physical energy content method

In compliance with international organisations (IEA, EUROSTAT, ECE) and the AG Energie- bilanzen (AGEB), the calculation of primary energy consumption was carried out with the ‘physical energy content method’.

In this method, hydroelectricity and other renewable energy carriers that cannot be attributed with a heating value (e.g. wind and solar electricity) are assigned ‘heating values’ that equal the amount of electric energy generated in the process. Thus, an ‘energy conversion efficiency’ of 100 % is assumed.

Furthermore, in the case of nuclear electricity production, heat from the nuclear reaction is the primary energy form. The energy conversion efficiency assumed for the generation of electricity from nuclear energy is 33 %.

Allocation of byproducts

In the case that several products arise in the process, energy consumption and emissions have to be allocated to the individual products, respectively.

In the case of cogeneration of heat and power plants (CHP), such as the supply of electricity from the electricity mix after [Nitsch et al 2012], the partial substitution method according to RED 2009/28/EC and [JEC 2011, 2013] is applied.

For the supply of biomass-based fuels, allocation of energy consumption and emissions is carried out in compliance with the stipulations of the RED 2009/28/EC in reference to the lower heating value of the primary product and byproducts. In the case that biofuel plants produce electricity as a byproduct, compliant with the RED 2009/28/EC the partial substitution method is applied. In this case, the byproduct electricity is substituted by electricity generated from the same energy carrier.

For the supply of petrol and diesel after [JEC 2013], a marginal approach is carried out, i.e. the calculation of the efforts required to provide an additional amount of fuel.

For LPG from natural gas processing, allocation was carried out according to energy content. For LPG derived from crude oil (refinery), allocation factored in the energy content of the refinery products (petrol, kerosene, diesel, LPG etc.) in reference to the respective refinery

Page 56 of 79 process after [ETSU 1996].

Embodied energy

The energy consumed in the construction of processing plants and vehicles (so-called embodied energy or grey energy) and the associated greenhouse gas emissions are not considered. Analyses with a similar scope, e.g. well-to-wheel analyses conducted by JRC/EUCAR/CONCAWE at the European level [JEC 2011] or the EU Renewable Energy Directive (RED 2009/28/EC) for the calculation of typical values, have adopted a similar policy. Embodied energy may be considered negligible in the electricity and fuel supply in general. As the proportions of renewable electricity and renewable heat increase, the energy emissions associated with the construction of plants, infrastructure und vehicles decrease. Exceptions to this general trend may be found when considering non-energetic environmental impacts, such as depletion of raw materials (mining).

Other impact categories

The environmental impacts investigated here include energy consumption, greenhouse gas (GHG) and pollutant emissions (Chapter 3.1).

As the proportion of fuels derived from biomass, tar sands and shale gas in the fuel mix increases, additional environmental impacts such as biodiversity, soil quality, water intensity and area demand become increasingly relevant. The analysis of these highly complex rela- tionships is beyond the scope of the present study. This may serve as a cautionary tale to illustrate that a single environmental indicator, such as the GHG emissions frequently ad- dressed in politics, science and society, reveals but a glimpse of the full picture. From a mathematical perspective, every single indicator is required, yet insufficient in isolation due to the associated risk of collateral damage to other environmental sectors.

Fossil fuels

Petrol and diesel from crude oil

For petrol and diesel produced from crude oil, the assumptions underlying the conclusions followed [JEC 2013], which updates [JEC 2011]. The pollutant emissions were adopted from [ETSU 1996]. The following tables illustrate the energy flows and emissions associated with the production of crude oil.

Page 57 of 79 Table 12: Energy flows and emissions from crude oil production

I/O Unit Amount Crude oil from field Input MJ/MJ 1.058 Crude oil Output MJ 1.000 Emissions

CO2 - g/MJ 3.8

CH4 0.0384

NOx - g/MJ 0.0097 Dust/PM - g/MJ

SO2 - g/MJ NMVOC - g/MJ 0.0112 CO - g/MJ 0.0015

Crude oil is exported to Europe for processing. Table 13 illustrates the energy flows and emissions arising from crude oil transport to the refinery.

Table 13: Energy flows and emissions from crude oil transport

I/O Unit Amount Crude oil Input MJ/MJ 1.000 Heavy fuel oil Input MJ/MJ 0.010 Crude oil Output MJ 1.000 Emissions

CO2 - g/MJ 0.8

NOx - g/MJ 0.015 Dust/PM - g/MJ 0.001

SO2 - g/MJ 0.015 NMVOC - g/MJ 0.001 CO - g/MJ 0.002

The consumption of heavy fuel oil (HFO) is linked to the supply of HFO.

Crude oil is processed to petrol and diesel in a refinery. The associated energy consumption and GHG emissions follow [JEC 2011], whereas the pollutant emissions are reported from [FEA 1999].

Page 58 of 79 Table 14: Energy flows and emissions from the production of petrol and diesel in oil refineries

I/O Unit Petrol Diesel Crude oil Input MJ/MJ 1.08 1.10 Diesel Output MJ 1.00 1.00 Emissions

CO2 - g/MJ 7.0 8.6

NOx - g/MJ 0.0072 0.0089 Dust/PM - g/MJ 0.0006 0.0006

SO2 - g/MJ 0.0103 0.0131 NMVOC - g/MJ 0.0094 0.0117 CO - g/MJ 0.0039 0.0047

The products petrol and diesel are transported to a fuel depot via pipeline, inland waterway vessel (distance 500 km) or rail (distance 250 km). The percentage of fuel transport modes is distributed as follows: via pipeline 60 %, via inland waterway vessel and rail 20 % each. Elec- tricity consumption for pipeline transport amounts to approx. 0.0002 MJ per MJ fuel. Fuel transport via ship requires about 0.012 tkm per MJ petrol and diesel over a distance of 500 km. Table 15 illustrates the energy consumption and GHG emissions of a typical inland waterway vessel derived from [EDU 1996]. Fuel calculation is based on a return trip (empty) per transport via inland waterway vessel.

Table 15: Fuel consumption and GHG emissions of an inland waterway vessel

I/O Unit Amount Diesel Input MJ/tkm 0.50 Distance Output tkm 1.000 Emissions

CO2 - g/tkm 36.9

CH4 - g/tkm 0.03

N2O - g/tkm 0.00

NOx - g/tkm 0.30 Dust/PM - g/tkm 0.03

SO2 - g/tkm 0.031 NMVOC - g/tkm 0.04 CO - g/tkm 0.17

Fuel transport over a distance of 250 km by rail requires approx. 0.0058 tkm per MJ petrol/diesel in transport. Rail electricity consumption amounts to approx. 0.21 MJ per tkm cov-

Page 59 of 79 ered by the EU electricity mix (10-20 kV level).

The electricity consumption of a fuel depot totals at approx. 0.0008 MJ/MJ fuel which is supplied by the EU electricity mix (0.4 kV level).

From the fuel depot, fuel is distributed to the fuelling station across a distance of 150 km. For this purpose, fuel is transported by lorry with a gross vehicle weight of 40 t and a transport capacity of 26 t petrol or diesel. The fuel consumption of the lorry is 35 l per 100 km.

The electricity consumption of the fuelling station amounts to 0.0034 MJ/MJ petrol or diesel.

Petrol and diesel from tar sands

The production of synthetic crude oil (SCO) from tar sands includes the mining of the bitumi- nous sand, extraction of bitumen and refining into synthetic crude oil fit for processing in conventional oil refineries.

The energy flows and emissions from the production of SCO from tar sands were adopted from [Renewbility 2009], and are based on data from Syn-Crude and SunCor in Canada. Bitumen from tar sands is applied as a feedstock for upgrading. To date, Syn-Crude is ex- tracting tar sands exclusively through strip mining on the surface, whereas SunCor employs surface mining as well as in situ application of solvents.

Table 16: Energy flows and emissions from the production of synthetic crude oil (SCO) from tar sand deposits in Canada

I/O Unit Amount Tar sands Input MJ/MJ 1.279 Crude oil Output MJ 1.000 Emissions

CO2 - g/MJ 19.1

CH4 - g/MJ

N2O - g/MJ

NOx - g/MJ 0.042 Dust/PM - g/MJ

SO2 - g/MJ 0.115 NMVOC - g/MJ 0.065 CO - g/MJ

Additional environmental impacts associated with the mining and processing of tar sand deposits include water pollution with toxic substances, hazards to drinking water and the altera- tion of large natural areas with consequences for biodiversity.

Bitumen extraction consumes between 2 and 4 barrels of water per barrel crude bitumen.

Page 60 of 79 Residues from SCO production are stored in open surface ponds (so-called tailings). The residues contain toxic components. Leakage may result in pollution of surface and ground water [Pembina 2009].

The SCO is transported to the coast via a 5000 km pipeline. The electricity consumption of the pipeline transport is approx. 0.0082 MJ per MJ SCO after [GEMIS 2005]. From the coast, the SCO is shipped to the EU per tanker over 6000 km. The oil tanker is operated with HFO with a sulphur content of 3.5 %. The specific energy consumption and emissions of an oil tanker (Table 17) were derived from [ESU 1996].

Table 17: Fuel consumption and GHG emissions of an oil tanker

I/O Unit Amount Heavy fuel oil (HFO) Input MJ/tkm 0.056 Distance Output tkm 1.000 Emissions

CO2 - g/tkm 4.3

CH4 - g/tkm

N2O - g/tkm

NOx - g/tkm 0.086 Dust/PM - g/tkm 0.004

SO2 - g/tkm 0.086 NMVOC - g/tkm 0.003 CO - g/tkm 0.011

In the EU, SCO is processed in a refinery close to the entry port. For refinery and distribution of the fuels petrol and diesel, the same assumptions were applied as for petrol and diesel produced from conventional crude oil (see previous chapter).

CNG from natural gas

Natural gas is extracted and processed in remote gas fields. The associated energy consumption and GHG emissions were estimated according to [JEC 2013]. Air pollution was derived from [ETSU 1996] and [Ecoinvent 2007].

Page 61 of 79 Table 18: Energy flows and emissions from the production and processing of natural gas

I/O Unit Amount Natural gas Input MJ/MJ 1.024 Natural gas Output MJ 1.000 Emissions

CO2 - g/MJ 1.65

CH4 - g/MJ 0.083

N2O - g/MJ 0.000

NOx - g/MJ 0.005 Dust/PM - g/MJ 0.000

SO2 - g/MJ 0.001 NMVOC - g/MJ 0.004 CO - g/MJ 0.001

The energy input is calculated in reference to the lower heating value, i.e. the energy input is inversely proportional to the efficiency.

Natural gas is conveyed from the gas field to the EU via a pipeline. Two pathways were included in the analyses:

Transport distance 4000 km

Transport distance 7000 km

Natural gas transport via pipeline across distances of 4000 km, or 7000 km, is associated with mechanical work of approx. 0.36 MJ/tkm [JEC 2013]. The lower heating value of natural gas is approx. 50 MJ/kg. Loss of natural gas through leakage along the transport route is estimated after [Wuppertal 2004]. Methane loss during long-distance natural gas transport is minor (< 1 % over 7000 km). The assumptions of [JEC 2013] approximately correspond with data from [Wuppertal 2/2008].

Table 19: Energy flows and emissions from transport of natural gas over great distances

I/O Unit 4.000 km 7.000 km Natural gas Input MJ/MJ 1.0052 1.0092 Mechanical work Input MJ/MJ 0.028 0.051 Natural gas Output MJ 1.0000 1.0000 Emissions

CH4 - g/MJ 0.104 0.184

Page 62 of 79 The mechanical work associated with natural gas transport in pipelines is performed with gas turbines operated with natural gas. The energy conversion efficiency of the turbine is estimated to be approx. 30 %. Energy consumption and emissions from mechanical work for natural gas transport are derived from [GEMIS 2011]. In [GEMIS 2011], natural gas transport from Russia to Germany in 2020 is assumed to be performed with a gas turbine efficiency of 32 %, which is similar to the 31.5 % assumed by [Wuppertal 2/2008] for 2030 (scenario with low natural gas production and low investment). The present study assumes a gas turbine efficiency of 32 % for the time horizon from 2020.

Table 20: Natural gas consumption and emissions from gar turbines of natural gas compressors

I/O Unit 4000 / 7000 km 4000 / 7000 km (2010) (2020) Natural gas Input MJ/MJ 3.333 3.125 Mechanical work Output MJ 1.000 1.000 Emissions

CO2 - g/MJ 183.6 171.9

CH4 - g/MJ 0.028 0.026

N2O - g/MJ 0.009 0.008

NOx - g/MJ 1.114 1.044 Dust/PM - g/MJ 0.028 0.026

SO2 - g/MJ 0.001 0.001 NMVOC - g/MJ 0.070 0.065 CO - g/MJ 0.557 0.522

Analogous to [JEC 2013], the regional fuel distribution is assumed to cover 500 km (high pressure natural gas pipeline), whereas the local distribution will not exceed 10 km (local natural gas grid) to the CNG fuelling station. Methane loss during distribution along the high pressure network amounts to approx. 0.0006 % according to [GEMIS 2006]. The required mechanical work of 0.003 MJ per MJ natural gas is performed with a gas turbine with an energy conversion efficiency of 31 %.

The electricity consumption of the CNG fuelling station is 0.026 MJ per MJ CNG in 2010, and 0.024 MJ per MJ CNG in 2020. Electricity is supplied by the grid.

LPG from crude oil/natural gas

In addition to methane (CH4), the gases extracted from a natural gas field contain portions of fuel gases such as ethane (C2H6), propane (C3H8) and butane (C4H10). During natural gas processing, propane and butane are isolated and traded as LPG (Liquefied Petroleum Gas).

Page 63 of 79 Energy demand and emissions for the production of LPG from natural gas processing are derived from ETSU [1996]. The data in [ETSU 1996] are reported in reference to the higher heating value (HHV) and were converted to the lower heating value (LHV)24. Table 21 illustrates the inputs and outputs for the extraction of LPG. The LPG input is equal to the LPG escaping from the gas field.

Table 21: Energy flows and emissions for the production and processing of LPG

I/O Unit Amount Natural gas Input MJ/MJ 0.053 LPG Input MJ/MJ 1.000 LPG Output MJ 1.000 Emissions

CO2 - g/MJ 3.1

CH4 - g/MJ 0.015

N2O - g/MJ 0.000

NOx - g/MJ 0.009 Dust/PM - g/MJ 0.000

SO2 - g/MJ 0.000 NMVOC - g/MJ 0.011 CO - g/MJ 0.001

For transport of LPG with small transport vessels, LPG is shipped in a compressed state. For transport of LPG in large transport vessels, LPG is liquefied through cooling to -48°C and stored in a cryogenic storage tank on board (the boiling point of LPG at a pressure of 0.1013 MPa is at -42°C).

Liquefaction of LPG through cooling requires 130 MJ of electricity per ton LPG [ETSU 1996]. Electricity is supplied by a combined cycle gas turbine plant (CCGT) operated with natural gas with an energy conversion efficiency of 58 %.

In the United Kingdom, LPG consists of a blend of approx. 90 % propane (volumetric) and 10 % butane (vol.) [ETSU 1996]. In Germany, LPG in the winter season consists of 60 % propane (vol.) and 40 % butane (vol.), whereas in the summer the ratio is reversed to 40 % propane (vol.) and 60 % butane (vol.). Thus, the average annual mix in Germany is 50 % propane and 50 % butane (vol.). This corresponds to 47 % (ener.) propane and 53 % (ener.) butane in reference to the lower heating value (LHV) in Germany.

24 LHV (Propane) = 50.0 MJ/kg; LHV (Propane) = 46.4 MJ/kg

Page 64 of 79 Table 22: Fuel qualities of LPG

Unit Propane Butane Lower heating value MJ/kg 46.35 (1) 45.74 (1) (LHV) 46.33 (2) 45.62 (2) Density at 15°C liquid kg/l 0.51 0.59 Composition in Germany Winter % vol. 60 40 Summer % vol. 40 60 Mean % vol. 50 50 % energetic 47 53 (1) Calculated; (2) [LBST 2010]

With an estimated LHV of 46.0 MJ/kg for the German propane/butane blend, the electricity consumption for liquefaction purposes amounts to approx. 0.0028 MJ per MJ LPG. The electricity demand is commonly met with a CCGT plant operated with natural gas with an energy conversion efficiency of 55 %

The capacity of the LPG transport vessel ‘Djanet’ by Kawasaki is 84,000 m³ LPG [Kawasaki 2000]. Another LPG transport vessel by Kawasaki, the ‘Grace River’, has a similar capacity of 79,200 m³ LPG (~45,000 t LPG) [Kawasaki 1/2002].

The majority of Japanese ports are equipped to discharge cargo from such LPG transport vessels [Kawasaki 2/2002]. The data for the vessel ‘Djanet’ were employed in the calculation of energy consumption and emissions in [JEC 2011].

Table 23: LPG transport vessel “Djanet“ [Kawasaki 2000]

Transport capacity (LPG) 84,310 m³ Speed 16.8 kn (31 km/h) Driving power (Kawasaki-MAN B&W 5S70MC Mk VI) 13,646 kW Fuel Heavy fuel oil (HFO)

At -42°C and 0.1 MPa, the density of propane is approx. 0.58 t/m³. At -48°C and 0.1 MPa, the density of propane is approx. 0.59 t/m³. The maximum fill factor is 0.98. Thus, with a nominal transport capacity of 84,310 m³, the ‘Djanet’ may ship approx. 47,900 t of LPG. The specific fuel consumption for the main engine system of the vessel (fitted with a two-stroke diesel engine) amounts to approx. 169 g per kWh of mechanical work ( 5 %) operated with fuel with a LHV of 42.7 MJ/kg hat. The total energy conversion efficiency amounts to 49.9 % [MAN 2003].

Page 65 of 79 Two options were included for the transport distance:

LPG from remote natural gas fields. One-way distance for LPG transport by ship: 5,500 nautical miles (10,186 km).

LPG from natural gas fields in the North Sea. One-way distance for LPG transport by ship: 1,000 km.

Large volumes of LPG are commonly stored in fuel depots under cryogenic conditions, i.e. at < -42°C [ETSU 1996]. The transport distance for lorry transport of LPG is assumed to average 500 km to the fuelling station.

Lorry transport of LPG is pressurised to retain liquid LPG. According to [SeAH 2003], the geometric volume of an LPG tanker lorry is approx. 43.5 m3. With a maximum filling factor of 0.85 and an LPG density of 0.5 t/m3, the total LPG to be loaded in one tanker comes to approx. 18.5 t LPG. The mass of the LPG tank amounts to approx. 8.6 t.

The estimated specific fuel consumption depending on payload is based on an assumed fuel consumption of 35 l diesel per 100 km. According to [KFZ-Anzeiger 2003], the average fuel consumption of a Mercedes-Benz Actros 1844 is 31.6 l diesel per 100 km. The preceding model, the Mercedes-Benz Actros 1843, had a fuel consumption of 34.9 l diesel per 100 km. The average fuel consumption of a different lorry, the MAN TG 510 A, is reportedly 37.0 l diesel per 100 km [KFZ-Anzeiger 2001]. The fuel consumption of a lorry with a payload of 25 t amounts to 32.8 l diesel per 100 km according to [ETSU 1996]. This corresponds to a specific consumption of 0.936 MJ/tkm assuming empty return. Thus, the estimate of 0.936 kWh/tkm is considered a realistic assumption for the present study.

Table 24 illustrates the fuel consumption and the emissions of a lorry with a gross vehicle weight of 40 t and a payload of 27 t, representing typical conditions for LPG transport by lorry. The lorry is classified Euro 4. The emission limits for heavy-duty vehicles are reported in g per kWh mechanical work. For the conversion in g/km, a cycle conversion efficiency of 37.5 % is assumed for diesel engines based on lorry manufacturer data.

Page 66 of 79 Table 24: Fuel consumption and emissions of a 40 t lorry

I/O Unit Amount Diesel Input MJ/tkm 0.936 Distance Output tkm 1.0000 Emissions

CO2 - g/tkm 68.6

CH4 - g/tkm 0.005

N2O - g/tkm 0.000

NOx - g/tkm 0.341 Dust/PM - g/tkm 0.002

SO2 - g/tkm 0.000 NMVOC - g/tkm 0.040 CO - g/tkm 0.146

LPG from the tanker lorry is transferred to a stationary pressure tank by simple overflow due to a pressure gradient. Thus, no additional electricity demand for compression arises. The electricity consumption of an LPG fuelling station is assumed to equal that of a regular diesel or petrol fuelling station. The electricity consumption of a diesel/petrol fuelling station amounts to approx. 0.0034 MJ per MJ diesel or petrol according to [TotalFinaElf 2002]. Anal- ogous to [JEC 2013], it is assumed that the electricity is supplied from the EU electricity mix, i.e. attributed emissions of 489 g CO2 equivalent per kWh electricity. Operation with the 25 German electricity mix (approx. 575 g CO2eq/kWhel after [UBA 2010a] , or estimate LBST for

2011 approx. 596 g CO2eq/kWhel) would result in slightly higher GHG emissions. With increasing percentages of renewable electricity in the German electricity mix, future GHG emissions from electricity supply are expected to decrease (LBST estimate based on BMU

Leitstudie 211 CO2eq/kWhel in 2030).

LPG is further produced in a number of processes during crude oil refining. For instance, LPG is extracted from light fractions resulting from atmospheric distillation, cracking processes (hydrocracker, FCC cracker) and visbreaking and coking, further as a byproduct of catalytic reforming (improvement of octane number) and subsequent processes.

25 [UBA 2010a] considers CO2 emissions only; emissions of CH4 and N2O may results in additional GHG emissions of 30 g/kWhel.

Page 67 of 79 Propane: 0.5 Mt Butane: 0.6 Mt

C1/C2 Light naphtha Isomerate Isomerization C4 & lighter H2 C3 C & lighter Gas 4 C4 & lighter Sep. iC4/nC4 Heavy naphtha Reformate plant Catalytic fractionation and reformer hydrogenation

H2S H2 H Butane 2 Reformate HDS Visbreaker Lt. naphtha Naphtha H2 Isomerate H2S H2 C4 & lighter Atm. Polymerisate Crude Gasoline distillation Lt. naphtha oil HDS Hydro FCC naphtha Visbreaker Kerosene 10 Mt Gasoline kerosine Cracker Heavy naphtha Diesel 2.8 Mt H S H 2 2 Kerosene C1/C2 C /C Diesel HDS 3 4 Diesel Visbreaker FCC FCC naphtha Heating Oil Diesel 40% diesel Diesel Heating Oil Atm. residue 3.6 Mt C4 & lighter H S H H S Vacuum 2 2 2 distillate To naphtha HDS Vacuum HDS distillation Visbreaker To kerosin HDS Claus plant Vaccuum residue To diesel HDS

Vaccum gas oil (0.1-0.7% S): Low sulfur fuel oil (0.1% S): Heavy fuel oil, Bunker C: S: 0.041 Mt 0.8 Mt 0.6 Mt 1.1 Mt Source: FZJ 1994, Acurex 1996, Scanraff 2002

Figure 19: Crude oil refinery

In a refinery, crude oil is converted to petrol, diesel, LPG and a number of other products. Refinery data was derived from [ETSU 1996].

Table 25: Energy demand and emissions from LPG production in a crude oil refinery

I/O Unit Amount Crude oil Input MJ/MJ 1.087 LPG Output MJ 1.000 Emissions

CO2 - g/MJ 7.0

CH4 - g/MJ 0.000

N2O - g/MJ 0.000

NOx - g/MJ 0.015 Dust/PM - g/MJ 0.000

SO2 - g/MJ 0.067 NMVOC - g/MJ 0.100 CO - g/MJ 0.001

Analogous to the assumptions for LNG in [JEC 2011], the average distance for LPG lorry transport to the fuelling station is assumed to be 500 km. LPG transport assumes the same Page 68 of 79 lorry data applied for the transport of LPG from natural gas processing, including the same assumptions for the fuelling station (see above in this chapter).

Renewable fuels

Biomethane

Methodology

The results for biomethane included in the present study are based on a number of published studies examining potential environmental effects of production and utilisation of biomethane as a fuel [Biogasrat 2011], [CML 2001]. The reported GHG emissions were derived from the Renewable Energies Directive [EU RED, 2009/28/EC] and the German Sustainable Biofuels Ordinance (Biokraft-NachV).

In principal, the calculation steps were uniform across the impact categories and selected pollutants (i) cumulative energy demand (CED), (ii) nitrogen oxides (NOX). (iii) non-methane hydrocarbons (NMHC) and (iv) sulphur dioxide (SO2). The cumulative energy demand was calculated employing the CML Impact Assessment Method [CML 2001]. The additional pollutants included are excerpts from the inventory results of the biomethane concepts under investigation.

Results

Table 26 summarises data for major environmental parameters of biomethane supply via biogas in contrast with future supply via gasification (bio-SNG). The inference of universal statements for entire fields of technology (e.g. biomethane production) remains difficult due to the fact that LCAs generally present specific case studies. The data for biomethane from renewable resources and waste materials reported in the table represent averages for typical plant concepts in new facilities operated with state-of-the-art facilities. For the examined pathways, the reduction potential for GHG emissions primarily depends on the utilised feedstocks, the supply of process energy and the extent of methane emissions during conversion.

Page 69 of 79 Table 26: Overview of data for ecological parameters of biomethane supply Scenario Concept Category Unit Electricity mix Electricity mix today 2030

GHG g CO2 eq/MJ fuel 39 26

Biomethane via CED non-renew. MJ/MJ 0.61 0.35 biogas from CED total MJ/MJ 2.99 2.80 renewable resources/liquid NHMC g/MJ fuel 0.01072 0.009726 manure NOx g/MJ fuel 0.080646 0.074362

SO2 g/MJ fuel 0.030723 0.020197

GHG g CO2 eq/MJ fuel 29 8.9 CED non-renew. MJ/MJ 0.69 0.25 Biomethane via biogas from bio- CED total MJ/MJ 2.24 1.9 degradable NHMC g/MJ fuel 0.004571 0.00300 waste NOx g/MJ fuel 0.03027 0.0203

SO2 g/MJ fuel 0.02420 0.00739

GHG g CO2 eq/MJ fuel 29 22 CED non-renew. MJ/MJ 0.39 0.28 Biomethane via CED total MJ/MJ 2.33 2.2 gasification (SNG 380 MW) NHMC g/MJ fuel 0.013 0.012 NOx g/MJ fuel 0.089 0.085

SO2 g/MJ fuel 0.05 0.04

Assumptions and references

An overview of the concepts for biomethane supply from renewable resources/liquid manure or biodegradable waste examined in the present study is presented in the following. A detailed description may be found in [Biogasrat 2011].

Supply concepts biomethane via biogas from renewable resources/liquid manure or biodegradable waste:

The size selected for conversion plants for the supply of biomethane from renewable resources/liquid manure and biodegradable waste was 1.2 MWel eq.

The renewable resources/liquid manure plant applied 64 % maize, 8 % cereal silage, 8 % grass and 20 % liquid manure.

The concept for biomethane production from biodegradable waste applied 50 % biodegradable waste and catering waste/residues from the food industry, respectively. For the purpose of maintaining a conservative calculation approach, supply of external process energy (ex-

Page 70 of 79 ternal electricity supply, heat supply via natural gas boiler) was assumed. Methane emissions from biogas production and upgrading were an estimated 2 % factored in the balance. Addi- tional relevant data on the examined production facility concepts are illustrated in Table 27.

Table 27: Parameters of the examined concepts for biomethane production from renewable resources/liquid manure and biodegradable waste [Biogasrat 2011] Unit Biomethane Biomethane from from renewable biodegradable resources/liquid waste manure

Substrate volume (renewable t/kWh resources/biodegradable waste) 0.00099 0.00096 incl. silage losses Hsbiomethane

Liquid manure volume t/kWh 0.00021 Hsbiomethane

Transport distance substrate km 15 15

Biogas volume Nm³biogas/a 4973317 4722262

Electricity demand biogas plant kWhel/kWh Hs bio- 0.0242 0.0804 methane

Heat demand biogas plant kWhth/kWh Hs bio- 0.0949 0.1185 methane

Biomethane volume Nm³biomethane/a 2703495 2703495

Electricity consumption pressur- kWhel/kWh Hs bio- 0.0514 0.0488 ised water washing methane

Full load hours h/a 8100 8100

Supply concept biomethane via gasification (bio-SNG):

The thermo-chemical conversion process of biogenic solid fuels into biomethane is structured in five successive stages: (i) drying, (ii) gasification, (iii) gas cleaning and conditioning (iv) methanation and (v) gas upgrading. In this process, dried biomass is converted into a flue gas consisting of CO2, CO, H2O, H2 and – depending on the conversion process – CH4 in a gasifier under application of a gasification medium (e.g. steam, oxygen). The resulting gas contains impurities including particulate matter, tars, sulphur and nitrogen compounds and halogens. These impurities have to be removed in a purification step before methanation. In the subsequent step, the hydrogen and carbon monoxide content in the purified gas is converted to methane and water in a synthesis reactor supported by a catalyst (methanation). The gas escaping during synthesis is high in methane. However, before infeed into the gas grid, gas upgrading, i.e. drying and removal of CO2, is required.

The bio-SNG concept examined in the present study is an advanced theoretical model based

Page 71 of 79 on the concept applied at the pilot plant in Güssing, Austria. The concept assumes a thermal input of 500 MW. Fuels in this concept include 65 % short rotation coppice, 25 % logging residues and 10 % cereal straw. A detailed description of the concept may be found in [DBFZ 2009].

Synthetic methane from renewable electricity (RE methane)

Electrolysis of water has been employed for the production of hydrogen for about 100 years. The first major electrolysis plant was established by Norsk Hydro in Norway in 1927 [Ullmann 1989]. Today, caustic potash (KOH) or proton exchange membranes (PEM) are used as electrolytes. In the first plant constructed in 1927, caustic potash served as electrolyte. Alka- line water electrolysis remains the most common technology. Advances in the field of PEM electrolysis technology include innovations by Siemens, currently developing PEM electrolysers with multi-MW output [Waidhas 2011].

Electricity consumption including all auxiliary power units (rectifiers, pumps, compressors, control units, gas processing if applicable) of recent electrolysers ranges between 4.3 and 5.2 kWh per Nm3 hydrogen. This corresponds to an energy conversion efficiency of 58 to 70 % in reference to the lower heating value of the resulting hydrogen. The present study assumed an electricity consumption of 4.5 kWh per Nm3 hydrogen. Hydrogen is supplied with a pressure exceeding 2 MPa (high-pressure electrolysis).

Methanation with CO2 is carried out in the subsequent step. The generation of methane from hydrogen involves the following reaction:

4 H2 + CO2 CH4 + 2 H2O (gaseous) H = -165 kJ

This is an exothermic reaction. The catalytic methanation is carried out at temperatures between 200 and 400°C in the presence of a catalyst based on Ni or Ru, Rh, Pt, Fe, and Co [Lehner 2012].

CO2 is assumed to be supplied by a biogas upgrader. Purification of biogas to pure methane produces high-purity CO2 during pressurised water washing and pressure swing adsorption (PSA). The only prerequisite required in this case is the compression of hydrogen from am- bient pressure (0.1 MPa) to the pressurisation level for methanation (0.5 MPa). Electricity consumption for CO2 compressions amounts to approx. 0.04 kWh per kg CO2. The CO2 demand of approx. 0.198 kg per kWh methane thus results in an electricity consumption of approx. 0.008 kWh per kWh methane associated with CO2 supply.

Page 72 of 79 Table 28: Input/output data for the production of methane from CO2 and hydrogen (incl. CO2 supply)

I/O Unit CO2 from biogas upgrading

CO2 Input kg/kWh 0.198 Electricity Input kWh/kWh 0.008

H2 Input kWh/kWh 1.200

CH4 Output kWh 1.000

An electrolysis energy conversion efficiency of 67 % in reference to the lower heating value of hydrogen results in the overall energy conversion efficiency of 56 % for CO2 derived from biogas upgrading.

In comparison, [Sterner 2009] state an energy conversion efficiency of 60 % in reference to the lower heating value for the production of methane from renewable electricity. However, the energy conversion efficiency of the electrolyser is reported at 76 % in reference to the lower heating value (LHV). This corresponds to approx. 87 % in reference to the higher heating value (HHV). The result appears to be rather high given the fact that the electricity demand of all associated auxiliary power units (pumps, ventilation, rectifiers etc.) and transfer losses due to ohmic resistance are supposedly factored in the calculation.

The resulting methane is transferred to CNG fuelling station via the natural gas grid. The electricity consumption of CNG fuelling stations amounts to 0.026 MJ per MJ CNG in 2012 and 0.024 MJ per MJ CNG in 2030. Electricity is supplied by the grid.

Page 73 of 79 Appendix III: Energy taxation for fuels

Table 29: GHG savings costs for energy tax benefits in comparison to petrol

Fuel Energy tax GHG emissions GHG savings costs in comparison to petrol in €/t CO eq in ct/kWh in g CO2 eq/km 2 Petrol 7.3 206 - LPG 1.3 188 2.256 CNG 175 1.263 Biomethane from biode- 1.4 gradable waste 69 286 Diesel 4.7 180 547 Source: Energy Tax Act. Values converted to ct/kWh. Own calculations.

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